Labour's shadow chancellor John McDonnell is "making policy on the hoof" to appease the Scottish National Party, according to one MP.
Mr McDonnell promised that his party would not block a second vote on Scottish independence during an appearance at the Edinburgh Fringe Festival.
He said the issue of whether to hold another independence referendum was for "the Scottish Parliament and the Scottish people to decide", which contradicts the stance once held by Jeremy Corbyn.
But Jim Fitzpatrick, the Labour MP for Poplar and Limehouse, said the shadow chancellor's pledge was an attempt to "buy SNP votes".
"When we had the election for Scottish Independence in 2014, it was said at the time it would be a once-in-a-generational referendum," Mr Fitzpatrick told talkRADIO's Julia Hartley-Brewer.
"John has clearly thrown that out of the window off his own back; although I suspect he has probably spoken to Jeremy."
SNP leader Nicola Sturgeon has said she would be open to a pact with the Labour Party if they could form a majority and "lock the Tories out of government”.
But Mr Fitzpatrick said a potential SNP-Labour pact would still not give them a large enough majority.
"He [John McDonnell] is trying to buy the SNP votes, next there will be the Lib Dems, I suspect we are about to promise a second referendum on proportional representation to get them and the other independents on side," he said.
"It needs to unite the whole of the House. They need to get Dominic Grieve and a couple of others on side."