Published: 14:03, 14 May 2019
| Updated: 14:03, 14 May 2019
The former defence secretary is among 13 senior Conservatives urging the Prime Minister to call a halt to Brexit talks with Labour.
The talks were set to resume today but there is increasing speculation that they may end without a deal.
Sevenoaks MP Sir Michael Fallon, whose constituency voted to leave the EU by 54.4% to 45.6%, signed a letter from 13 former cabinet members, calling on the Prime Minister not to compromise with Labour over a customs union.
The letter said any deal that was agreed could be ditched by her successor and a compromise would lose the support of Conservatives who previously backed the deal.
It said: "More fundamentally, you would have lost the loyal middle of the Conservative Party, split our party and with likely nothing positive to show for it. No leader can [bind] his or her successor, so the deal would likely be at best temporary, at worst illusory."
Sir Michael told BBC Radio 4's Today programme: “This is a blind alley taking us into a customs union.We said we would leave a customs union very clearly at the time of the election. If you go into a customs union you can’t start pursuing independent trade deals.
“Far better to start concentrating on the other side which is the arrangements in Northern Ireland. The talks are clearly not getting anywhere. If they are going to include permanent membership of the customs union, then frankly we would be better off staying in the EU.
“Whether you believe in leaving or not, if you do leave you need to have the benefits of negotiating your own trade deals. Staying inside the customs union doesn’t allow you to do that. I fear the Prime Minister is misreading the mood of the Parliamentary party."
The intervention comes at a sensitive time for the government with potentially heavy defeats looming in elections for the European Parliament.
Labour leader Jeremy Corbyn used a speech launching the party's manifesto for those elections to put the party on alert for a general election sooner rather than later.