Jeremy Corbyn has been accused of betraying the party’s Brexit policy by the delegates who wrote it, as they demand he finally backs a Final Say referendum on Brexit.

The delegates from around the country have sent a letter to the Labour leader, directly charging him with failing to implement the plan carefully formed and approved by conference last year.

In a stinging rebuke they remind him that he promised “policy will be made by Labour members, not the leader”, but then go on to say, “the complete opposite now appears to be happening”.

A series of recent incidents have pushed Labour unity over Brexit to its limits, with the leader’s office and Brexit spokesman Sir Keir Starmer at loggerheads, prominent backbenchers warning over a collapse in support and rumours of some MPs forming a breakaway group.

The letter seen by The Independent was written by 23 constituency Labour party delegates who took part in a six-hour compositing meeting in September last year which set Brexit policy.

Delegates' Brexit letter to Jeremy Corbyn Show all 3 1 /3 Delegates' Brexit letter to Jeremy Corbyn Delegates' Brexit letter to Jeremy Corbyn Delegates' letter to Corbyn page 1 Delegates' Brexit letter to Jeremy Corbyn Delegates' letter to Corbyn page 2 Delegates' Brexit letter to Jeremy Corbyn Delegates' letter to Corbyn page 3

That policy included a commitment to Sir Keir’s “six tests” for a Brexit deal and also the line: “If we cannot get a general election Labour must support all options remaining on the table, including campaigning for a public vote.”

But the letter to Mr Corbyn explains that the delegates are writing because of “the failure of some of the party leadership team, including you, to adhere to all elements of this policy”.

The delegates point out that a list of demands Mr Corbyn recently made to Theresa May, which if met could secure his cooperation on a Brexit deal, excluded the most critical of Sir Keir’s six tests – that any deal the party signs up to delivers the “exact same benefits” as membership of the single market.

They go on to say: “You were elected leader of our party on a platform of transforming Labour into a member led movement. You said that ‘policy will be made by Labour members, not the leader, shadow cabinet or parliamentary party’.

You said that ‘policy will be made by Labour members, not the leader, shadow cabinet or parliamentary party’. Yet the complete opposite now appears to be happening Labour delegates letter to Jeremy Corbyn

“Yet the complete opposite now appears to be happening. I am sure you can appreciate our confusion and dissatisfaction with the current situation.

“Based on the content of your letter to the prime minister, not only is the policy not now being followed, it has clearly been changed – but without any mandate from the party membership to do so. How is this ‘Straight Talking, Honest Politics’?”

The delegates say they are a group made up of both long-standing members and others who were inspired to join the party by Mr Corbyn himself.

But with 29 March fast approaching, they warn that time is running out and emphasise that Labour’s efforts to secure an election have not been successful, and that the only remaining option is a new referendum.

They add: “The vast majority of the membership want a referendum on the deal. If we are truly a member led party, then all elements of the Brexit policy must be adhered to.

Brexit : What happens in the wake of another government defeat?

“There are no more options on the table other than calling for a referendum on the PM’s deal.”

A spokesman at party headquarters said: “The Labour Party is faithfully following our policy on Brexit."

A source in the leaders office argued that Mr Corbyn's five demands to Theresa May were consistent with Labour's conference policy, a Labour amendment put down in the commons on 29 January and Sir Keir's six tests.

He added: "While [Mr Corbyn's letter of demands to Theresa May] did set out more detail of a Brexit deal Labour could support it did not rule out the option of Labour campaigning for a public vote."

On Thursday, shadow treasury spokesman Clive Lewis MP, on the party’s left wing, broke ranks to criticise the Labour leadership for its “dangerous” failure to oppose Ms May’s exit plan full-on – warning it would keep the party out of power.

“My fear is that what we are now doing is that we are helping to facilitate a Tory Brexit,” he told a meeting of Labour supporters in Westminster.

Inside the commons chamber shortly after, pro-EU MP Chris Leslie, from the party’s right wing, gave a heavily critical speech on the leader’s position.

He pointed out that the words giving the commitment to an “option of a public vote” were absent from Mr Corbyn’s proposed amendment in parliament, adding: “I ask myself why are we regressing when it comes to our party’s policy, as passed at the September conference.”

Jeremy Corbyn hits out at Theresa May over post-Brexit shipping contracts at PMQs

Mr Leslie said he found it “heartbreaking” that the party was not fully opposing the Conservative plans for Brexit, and that frontbenchers were abstaining in key votes.

He went on: “On this particular issue, we are being played for fools by the leadership of the Labour party.

“By now, we should have reached the stage of a public vote on the option of remaining in the European Union.”

On the same day rumours swirled that some Labour MPs were about to announce that they would break from the opposition whip and form a new party.

Though it was denied and a break is yet to have materialised, the rumour persists and many expect it to happen at some point in the near future.

On Wednesday Neil Coyle MP claimed the party was losing members and councillors, and could yet lose MPs over its Brexit policy, while Wavertree MP Luciana Berger has said young voters would see the party as “standing in the way” of them having a say unless it backed a new referendum.

Earlier in the week, there were further signs of division at the top of the party when the leader’s spokesman was forced to reiterate that pushing for a new election is the Labour’s preference after Sir Keir indicated that a compromise deal or a new referendum were the “only credible options now left”.