The Liberal Democrats have accused the Tories of "going soft" on Scottish independence after leader Ruth Davidson said the UK Government should not block a second independence referendum.

Scottish Liberal Democrat business manager Mike Rumbles said he was "astonished by the U-turn" and questioned how the Tories' "completely weak position" would prevent another referendum.

In the Conservative manifesto, Ms Davidson said: "To those who want to ensure that strong opposition they know our country needs, I make this promise: If you vote for me and my team ... I will fight against any attempts to drag our country back to a second independence referendum."

She added: "We will oppose any attempt by the SNP to hold a second referendum during this parliament - no matter the result of the EU referendum this June."

READ MORE: Alex Salmond raises prospect of Tony Blair being tried for war crimes in Scottish courts

However, when asked if the UK Government should allow a future independence vote on BBC Sunday Politics Scotland, Ms Davidson said: "I would argue as strong as I could that we should stay part of our biggest market and closest friend. Constitutionally, the UK Government shouldn't block it, no."

Mr Rumbles said: "In the last election, the Conservatives claimed that they would provide strong opposition and were the only ones that could be trusted to block a second referendum.

"Every leaflet they issued said 'No to a second referendum'. There weren't any ifs or buts.

"Now, Ruth Davidson says that the UK Government shouldn't seek to prevent a second referendum.

"How will she explain this completely weak position to those who voted Conservative to prevent a damaging second referendum?

"With Ruth Davidson's admission yesterday, any pretence that they were providing strong opposition and would oppose a second referendum is also gone."

READ MORE: The coup against Corbyn was planned to stop him calling for Blair’s head after Chilcot

Liberal Democrat leader Willie Rennie has previously said there must be a mechanism for another referendum if Scotland expresses a desire for a re-run.

However, he said Ms Davidson "must not be allowed to get away with saying something before the election and then making a complete turnaround afterwards".

READ MORE: Alex Salmond raises prospect of Tony Blair being tried for war crimes in Scottish courts

He told the Press Association: "Before the election, Ruth was robustly against the idea of having another referendum and said she would provide a strong opposition and oppose independence at every step.

"Then as soon as the election is over, she says she will not block another referendum.

"Her rhetoric does not match her actions and she must not be let off the hook."

A spokesman for the Scottish Conservatives said: "As we said in the election campaign, and in parliament last week, there is no justification whatsoever for a second independence referendum."