Nigel Farage has almost total control over the new Brexit Party, with power to appoint its governing board and all but no membership to keep him in check, it is understood.

The party – which polls suggest could win the European elections – formed in January and registered last week. While more than 100,000 people have signed up to be registered supporters, it is not yet allowing them to become formal members with power to vote on the leadership.

It is understood only a handful of people have actual membership of the Brexit party, which is a skeleton operation as it gears up to fight its first election at the European polls.

The party’s constitution, released under freedom of information laws, also reveals Farage’s power over the project, with the leader having the ability to appoint four to eight board members and the chairman.

The setup suggests Farage is seeking to avoid the tussles he previously had with the Ukip national executive committee, which was elected by the membership.

It is understood the Brexit party has had more than 1,000 expressions of interest from people wanting to become candidates in the European election, and it is not planning to guarantee places on its list to former Ukip MEPs who defected to the Brexit party.

There are 14 MEPs listed as belonging to the Brexit party on the European parliament website but a party source said probably only five or six would be included in a final list of 70 candidates spread throughout the regions.

The party has announced at least five candidates – including Farage himself, John Longworth, a former director of the British Chambers of Commerce, Annunziata Rees-Mogg, the sister of the Conservative MP Jacob Rees-Mogg, and Ben Habib, a former Conservative donor. It is expected to unveil many more at a launch event on Tuesday.

Despite its lack of infrastructure, two polls by YouGov have put the Brexit party in pole position to win the European elections with between 17% and 23% of the vote, while Ukip has fallen back as it moves to the far right under the leadership of Gerard Batten.

A separate ComRes poll put Labour far away in first place to win the European elections, on 33%, with the Brexit party on 17%.

Farage told the Sun he “won’t get excited about one poll” but that it had been a “great first week for the party”.

All the polls show the Conservatives have taken a huge hit after failing to take the UK out of the EU on 29 March or 12 April, or to come up with an alternative to Theresa May’s Brexit deal.

Labour is considering applications from a number of pro-EU candidates to stand in the European elections. The Labour peer Andrew Adonis is understood to be second on the candidates’ list in the south-west, which is highly winnable, and Eloise Todd, of the Best for Britain campaign, is attempting to stand in Yorkshire.

However, some Labour MPs representing leave seats, such as Gareth Snell, have warned it would be a “strategic error” to offer up only MEPs in favour of a second referendum and campaigning to remain.

The Brexit party has been described by the SNP’s Pete Wishart as “Farage’s ego trip party”. It was originally founded and led by Catherine Blaiklock but she resigned over having repeatedly retweeted posts from far-right figures.

The party is now led by Farage, with two little-known figures acting as officers – Tracy Knowles as nominating officer and Phillip Basey as treasurer. The constitution shows the leader will be in post for a four-year term and can be removed only by a motion of no confidence voted on by the board, backed up by an extraordinary general meeting of members.

The party’s registered office is a serviced office in Victoria Street, Westminster, but it is known to have built up a war chest of cash through small donations of less than £500 on PayPal, which do not have to be declared, the £25 subscriptions of registered supporters and £100 applications from people who want to be MEP candidates.

Sajjad Karim, a Conservative MEP, attacked the PayPal method of donations in a speech in the European parliament this week, saying: “PayPal through donations of under £500 is facilitating the donations of money to Nigel Farage and I ask him to come and explain to this house. Nigel Farage, where is your money coming from?”

Batten, whose party has collapsed in the polls in recent days, attacked the Brexit Party at Ukip’s election launch on Thursday. He said his predecessor as Ukip leader had launched a “vehicle for one man” and added: “All you get from Nigel is rhetoric.”

The Brexit party declined to comment.

Meanwhile, there was extreme gloom among Conservatives about their plummeting position in the polls, which the ComRes chief executive, Andrew Hawkins, said was “the lowest Tory support I can remember in 16 years in this job”.

Matthew Goodwin, the University of Kent politics academic, said the numbers suggested it “could be the Tories’ annus horribilis” as they were “11 points adrift of Labour and what would be their lowest vote share in history”.