The snap general election called by Theresa May is Britain's chance to avoid a "disastrous hard Brexit", the Liberal Democrats have said.

Party leader Tim Farron told voters "this is your chance to change the direction of your country" after the Prime Minister called an early vote on June 8.

The Lib Dems have consistently called for a second referendum on the final Brexit deal Mrs May achieves after negotiations with the European Union, and want to keep the UK in the European single market.

Read more: Theresa May calls surprise general election as announcement stuns Westminster

The Tories' 2015 general election victory saw the party gain several formerly Lib Dem seats in the south-west of England.

Mr Farron said: "This election is your chance to change the direction of our country.

"If you want to avoid a disastrous hard Brexit.

"If you want to keep Britain in the single market. If you want a Britain that is open, tolerant and united, this is your chance.

"Only the Liberal Democrats can prevent a Conservative majority."

Green Party co-leader Caroline Lucas welcomed an early vote at a time when "Britain is at a crossroads" and said the people should be given a say over the country's future direction

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She promised the Greens would present a "bold, positive vision for a different kind of Britain".

"At this election we will stand for an economy that works for everyone, not just the privileged few; a Britain that's open to the world and the protection of our precious environment," Ms Lucas said.

"We will stand up to the politics of hatred and division that is scarring our communities and give people across the country a chance to vote for a better Britain."

Her co-leader, Jonathan Bartley, said the announcement of a snap election, following a string of denials there would be an early vote, revealed a "deep dishonesty at the heart of government".

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Professor Martin Smith, head of the University of York's politics department, said: "There is a danger that the Prime Minister's decision to call a snap election may appear both cynical and hypocritical.

"She had indicated several times that she would not do so and in order to do so she has to shift away from fixed term elections introduced by her predecessor.

"Clearly the reason for the election is that with Labour so weak in the polls, it is an opportunity for the Conservatives to win a landslide victory.

"With a large Conservative majority, the government will be able to get through any Brexit deal.

"Of course, there are going to be several difficulties for the Conservatives in the election campaign including the impact on Scotland and the potential for a second referendum, and a focus in the campaign on what sort of post-EU Britain the Conservatives want."

Ukip leader Paul Nuttall said: "We welcome the opportunity to take Ukip's positive message to the country.

"However, we believe that the Prime Minister's decision to call this election is a cynical decision driven more by the weakness of Corbyn's Labour Party rather than the good of the country.

"There is also the prospect of a slew of Tory held by-elections caused by the seeming systematic breach of electoral law at the last election, predominantly in places where Ukip were pressing the Conservatives hard.

"We are in the midst of Brexit negotiations so this election will provide a perfect opportunity for the 52% to vote for Ukip, the only party wholeheartedly committed to a clean quick and efficient Brexit."

Read more: Theresa May calls surprise general election as announcement stuns Westminster

Conservative stalwart Sir Malcolm Rifkind said: "I would not be honest if I didn't say I was not surprised, but I think the Prime Minister inevitably found it irresistible.

"I think we already know she's going to win the election, what we don't know obviously will be the size of the majority.

"I think the risk she's running is a manageable risk but it's there.

"Will the Liberal Democrats make a revival at the expense of some Conservatives?"

The former foreign secretary and minister for Europe went on: "There isn't a credible alternative government, even the Labour Party will not be claiming to win the general election, their best hope would be to end up more or less where they are at the moment."

Nigel Evans, Conservative MP for Ribble Valley, said he was looking forward to the early election.

He said: "When you look at the choice the British people is going to make on June 8 it is a Conservative government led by Theresa May or a Labour government led by Jeremy Corbyn, I don't think it's much of a gamble or a brave decision by the Prime Minister.

"I think she's seen that she's got a very strong lead in the opinion polls, she looks at the majority she's got at Westminster now which is very narrow, she wants a bigger majority in order to be able to go to Brussels and negotiate with (Donald) Tusk and (Jean-Claude) Juncker in order to deliver the Brexit result that's going to be in the best interests of the UK.

"I don't think it's a brave decision at all."

London Mayor Sadiq Khan said: "The British people will now have the opportunity to give their verdict on this Conservative Government - a Government that has prioritised a hard Brexit which puts our economy at risk, while implementing damaging policies that are entrenching inequality.

"I will be fighting hard for every Labour vote over the coming weeks - a Labour government is in the best interests of all Londoners and the whole country."

Shadow home secretary Diane Abbott said Mrs May had decided to "cut and run" and predicted an unpleasant campaign.

"People have got to make a choice between Theresa May's Britain and Jeremy Corbyn's Britain. They need to make a choice between an unpleasant, xenophobic hard Brexit and a Brexit that will protect jobs and living standards," she told BBC Radio 4's World At One.

"There is no question in my mind that the Tories will fight a very unpleasant campaign and the electorate's going to have to make a choice."

Plaid Cymru leader Leanne Wood said her party will contest every seat in Wales in the June election.

"The British Government has committed our country to a path of extreme economic recklessness," said Ms Wood. "It doesn't have to be their way. Wales needs MPs who will stand up to the Tories and be the voice of reason in Parliament, defending our country's vital economic links with Europe and the rest of the world.

"Plaid Cymru is united and we're up for the opportunity to advocate for Wales' best interests. The more Plaid Cymru MPs, the stronger Wales' voice will be.

"The official opposition is divided and unable to agree a position on the most important of decisions. Plaid Cymru in Westminster will stand up for our interests and make sure the decisions being taken now are made with future generations in mind, and not to cynically appease the extreme right wing of the Tory party."