Nigel Farage today makes a dramatic admission that the vote for Brexit could be overturned because Remainers have seized control of the argument over Britain’s future relationship with the EU.

The former Ukip leader told the Observer that he was becoming increasingly worried that the Leave camp had stopped fighting their corner, leaving a well-funded and organised Remain operation free to influence the political and public debate without challenge.

“The Remain side are making all the running,” said Farage. “They have a majority in parliament, and unless we get ourselves organised we could lose the historic victory that was Brexit.”

On Thursday Farage angered many Brexiters, and many in Ukip, when he said he was coming round to the view that the country might need to hold a second referendum in order to close down the EU argument for good.

Play Video 0:44 Nigel Farage backs second referendum on Brexit – video

He said then that he believed such a vote would see the Brexit side win with a bigger majority than the one it achieved on 23 June 2016, when it triumphed by 52% to 48%. But, speaking on Friday, Farage appeared to change his tune, making clear that he was seriously worried that Brexit could be undone and reversed. The case for a complete break from the EU was no longer being made, even by pro-Brexit MPs in parliament, he said.

Instead, the Remain camp was relentlessly putting out its message that a hard Brexit would be ruinous to the British economy and bad for the country, without people hearing the counter-argument that had secured Brexiters victory in the 2016 referendum campaign.

His latest intervention comes ahead of another vital week for the Brexit process in the House of Commons and as peers in the overwhelmingly pro-Remain House of Lords prepare to argue for retaining the closest possible links with the EU – and in some cases for a second referendum – when legislation reaches peers at the end of this month.

The clock is ticking and the time for sitting on the fence is long gone Chris Leslie MP

Farage said he now had a similar feeling to the one he had 20 years ago when Tony Blair appeared to be preparing the country for an eventual entry into the euro. “I think the Leave side is in danger of not even making the argument,” he said. “The Leave groups need to regather and regroup, because Remain is making all the arguments. After we won the referendum, we closed the doors and stopped making the argument.”

Last Monday Farage held a meeting in Brussels with the EU’s chief Brexit negotiator, Michel Barnier, which, he said, left him convinced that the UK would not be offered the kind of deal that would be easy to sell as beneficial to the UK economy unless Leavers upped their game.

“We no longer have a majority in parliament. I think we would lose the vote in parliament,” Farage said.

Farage’s rallying call to Leavers reflects genuine alarm among hardline Brexit supporters that too many concessions have already been made to the Remain side of the Brexit argument by Theresa May’s government, and that more could follow.

As negotiations continue in Brussels, and Brexit legislation passes through parliament, the government has already accepted the case for a two-year transition period in which the UK would effectively remain in the single market and customs union. Before Christmas, pro-EU Tory MPs sided with opposition MPs to defeat the government and ensure that MPs will have a “meaningful vote” on the eventual Brexit agreement struck with Brussels – meaning they have an effective veto.

Labour will back an amendment to the EU withdrawal bill demanding that a very detailed independent economic analysis of the effects of the eventual deal should be conducted after it is struck but before it is put to a vote of MPs.

While the Labour leadership is playing down the significance of the move, many MPs see it as a step towards their party backing permanent membership of the EU single market and customs union.

Labour MP Chris Leslie, a supporter of the pro-EU grouping Open Britain – one of those which Farage worries has become too influential – said: “The very least the Labour front bench should be supporting is a proper analysis of the dire economic consequences of leaving the single market and the customs union. The clock is ticking and the time for sitting on the fence is long gone. This should serve as a stepping stone to the party backing the position of staying in the single market and the customs union permanently.”

Anti-hard-Brexit Tories says their numbers have increased since May’s widely criticised government reshuffle, in which Remainer Justine Greening left the cabinet to sit with pro-EU Tories at prime minister’s questions.

Q&A What is a soft Brexit? Show Hide A soft Brexit, while not officially defined, would keep Britain in either the single market or the customs union or both. It could be achieved along the lines of the Norway model (see EEA/EFTA) or via an FTA, but would require concessions on free movement, ECJ jurisdiction and budget payments. Brexiters do not consider a soft Brexit as really leaving the EU. See our full Brexit phrasebook.

Writing for the Observer, Ben Bradley, the 28-year-old Mansfield MP and newly appointed Tory vice-chair for youth, said the reshuffle marked a moment for the party to show it would become more responsive to the needs of young voters following its poor election result last June.

“Last year’s general election saw a surge in young people turning out to vote, with 18-to-24-year-olds voting in greater numbers than at any other time,” he writes. “Politicians – of all political stripes – have to start listening. The fact that most of the youth vote went to Labour in 2017 means that Conservatives have to start listening even more carefully.

“As a young person – brought up on the values of tolerance and respect – I want to ensure that people of my generation and younger are not scared to say that they are a Conservative.”