THERESA May needs a larger Commons majority to avoid being held to ransom by “Brexiteer bastards” in her own party, Ruth Davidson has acknowledged.

The Scottish Tory leader said if the Prime Minister added to her MP tally in June, she could avoid the kind of infighting over Europe that destabilised Sir John Major in the 1990s.

Sir John faced constant pressure from a hard-right Eurosceptic faction of Tory MPs he labelled “bastards” while Prime Minister.

The comments undermined Mrs May’s own explanation for calling a snap election - opposition from the SNP, LibDems, Labour and the Lords over Brexit, rather than feuding in the Tories.

Launching the Scottish Conservative council election manifesto in Edinburgh, Ms Davidson said she agreed with Home Secretary Amber Rudd, who suggested on Tuesday that a bigger majority would give Mrs May more flexibility over the type of Brexit deal she could strike.

With a working majority of 17, Mrs May is at the mercy of hardline Eurosceptic MPs in her party who could rebel if they felt she was negotiating too soft a Brexit with Brussels.

However their influence would be diluted in a bigger Tory majority, potentially allowing the Prime Minister to make more compromises and maintain stronger EU links.

Agreeing with Ms Rudd, Ms Davidson cited “the experiences of John Major trying to steer through really complex questions about Europe when you have a very small majority”.

She said: “It allows a very small number of people to influence the debate in a way that might be unrepresentative of a wider Conservative party and wider mood within the country.

“I think if the Prime Minister is returned with a healthier majority, it gives her the freedom to make decisions in the best interests of the country, without having to pay a penalty in terms of people within either the Conservative party or outwith trying to put undue pressure on her.”

Asked if that meant Mrs May “wouldn’t be held to ransom by these Brexiteer bastards”, Ms Davidson replied: “I don’t know how to answer that without getting myself into a lot of trouble... but I’m not disagreeing with you.”

Ms Davidson also encouraged Labour and LibDem supporters to vote tactically for her party if their priority was stopping a second independence referendum and staying in the UK.

Although not a “particular proponent” of tactical voting, she said the Tories were best placed to thwart Nicola Sturgeon and insisted there was “no way the SNP is getting 56 this time”.

SNP Westminster leader Angus Robertson has called June's election a “two-horse race in Scotland between the SNP and the Tories”, dominated by the constitution.

Responding, Ms Davidson said: “It is certainly the case that we are the strongest party to take on the SNP. I think if you do believe in tactical voting and and if your principal belief (is in) keeping the United Kingdom together and respecting the decision that we made in 2014, actually your vote is for the Scottish Conservatives.

"If you're not supporting the SNP and you want someone to stop their drive to break up Scotland, then the Scottish Conservatives are your best bet."

She said she expected three of four Tory MSPs to stand in June, but ruled herself out.

"I am in charge of our candidate selection, our manifesto. I am in charge of our campaigns, our budgets, our targeting, our ground troops. This is my election."

Ms Davidson rejected Ms Sturgeon’s claim that Mrs may wanted to move the UK to the right.

The opposite was the case, she said.

“When you see the UK party manifesto, you will see a very centre-right document that has issues that we’ve already seen matter a lot to the Prime Minister, issues on fair working practices, issues around situations like modern slavery, issues that I think would be very hard for Nicola Sturgeon to suggest is the Conservative Party moving to the right.”

She predicted the local elections offered a litmus test of public opinion and predicted the Tory vote would go up, giving her party “a springboard into the general election”.

The local election manifesto contains pledges on schools, business rates and housing.

Scottish Labour local election manager Alex Rowley said Ms Davidson’s party planned “further spending cuts and privatisation if they get into councils around Scotland”.

Green candidate Yvonne McLellan said voters would “see through the Tories’ shameless attempt to turn the council elections into a vote on the constitution”.