The Conservative Party has suffered a collapse in the income it draws from membership fees, official data has revealed.

The party’s accounts show money the Tories earn from their membership plummeted by more than 40 per cent in 2017.

By contrast, membership income for the Labour Party grew by around 12 per cent, while the Liberal Democrats saw theirs rise by almost a third.

The drop in fees comes amid ongoing concern within the Conservatives about the party’s dwindling activist base, not to mention a new entryism threat from supporters of the Brexit-backing Leave.EU group.

Accounts filed with the Electoral Commission and published on Wednesday shine a light on the size of the Conservatives’ rank and file.

The papers produced by the party’s campaign headquarters show that in 2016 the Tories received slightly less than £1.5m from its membership, but that this figure dropped by some 43 per cent to just £835,000 in 2017 – the year Theresa May lost the party’s majority at an election.

The bulk of the Conservatives’ £45.9m income came instead from more than £34m worth of donations – a large increase of more than 80 per cent in the election year – with chunks coming from wealthy backers. Legacies that the party received from people leaving money in wills also rose, from £300,000 to £1.7m in 2017.

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The Labour Party’s account showed that it took just over £14m from its membership in 2016, rising to more than £16m in 2017 – an increase of 12 per cent.

The figures also saw the money it gained from donations increase by about 25 per cent to more than £18m in 2017.

The Liberal Democrats’ accounts showed money the party makes from its membership jump by some 32 per cent to almost £1.3m, with donations jumping 16 per cent to £6.1m.

Ukip membership income also plummeted 39 per cent to £560,000, the SNP’s fell marginally by a little over nine per cent, and the Green Party’s grew by about three per cent.

At the start of 2018 former Tory chairman Grant Shapps said that his party’s refusal to admit to its plunging membership was “embarrassing”.

He urged the prime minister to “come clean” about how few people are paid-up members, after one campaigner suggested the figure is as low as 70,000 though most estimates put it around 100,000.

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In stark contrast, Labour membership is growing and has now surpassed some 560,000.

The pro-Brexit Leave.EU group, founded by Arron Banks, recently began encouraging its members to join the Tories ahead of any future leadership contest, and amid speculation that Boris Johnson is preparing for a bid at the top job on a pro-Brexit platform.

The group claims to have 88,000 supporters, and is urging them to “flood” the Tory Party to elect a “true Brexiteer” such as Mr Johnson or Jacob Rees-Mogg.