Seeking a transitional arrangement with the EU that keeps Britain in the single market and customs is “wishful thinking” and “essentially kicking the can down the road”, Sir Vince Cable has said.

The Liberal Democrat leader said such a deal “is not going to be on offer” after Brexit, given it assumes the UK could do as it pleases.

It comes after deputy leader Jo Swinson said a Brexit transition deal could be used as a strategy to reverse EU withdrawal.

A number of leading Conservative and Labour MPs have suggested a transitional arrangement after Brexit that maintains Britain’s current trading relationship with Europe, in order to avoid a cliff-edge.

Sir Vince told the Press Association: “I think people in the Tory Party and the Labour Party, in perfectly good faith, have put forward this idea of a transitional arrangement. But it is essentially kicking the can down the road.

“At some point you’re either in or out, and the problem is when people talk about a transitional arrangement, they usually mean the British Government will do what it likes, and we’ll keep all the benefits of the single market and customs union.

“That is not going to be on offer, and I think a lot of this stuff of transitional agreements is actually wishful thinking.”

The former business secretary said it was very difficult to see how Brexit was going to be a success, with compromise options between a hard and soft Brexit “looking more and more difficult”.

Ms Swinson had earlier told a fringe meeting at the party’s Bournemouth conference that working with pro-European Tories and Labour on temporary post-exit trade arrangements would not be “giving up”, but would keep the door open to EU membership.

Ms Swinson said a transition deal after official EU withdrawal in March 2019 would give business more stability and allow the country space to think again on Brexit.

“What transition periods also do is they give time. They mean that it is not this mad rush and there is the opportunity there for the country to take stock and to think.

“The closer we are to our EU neighbours, the easier it is, at some future point, to reverse the decision.

“Because, if you haven’t then hugely diverged from everything, if you have still got the same rules in place, if you have still got the same trading arrangements, then actually the coming back becomes much easier. So, I think, strategically, that is important for us to try to achieve working with others.”

Chancellor Philip Hammond has said the Government is seeking a transition arrangement for a set amount of time that would “look a lot like the status quo”.

Brexit Secretary David Davis has ruled out joining the European Free Trade Association, which allows full access to the single market but means acceptance of some, though not all, EU law and regulation, without voting rights.