The Conservative MP David Davis has attacked parts of the government’s trade union bill, suggesting proposed restrictions on pickets were like something out of Franco’s dictatorship in Spain.

The MP, who ran against David Cameron for the Tory leadership in 2005, said he agreed with most of the bill.

However, he said some measures were draconian, including the requirement for picketers to give their names to the police.

The main point of the bill is to introduce a 50% turnout requirement for industrial action ballots, and a minimum positive vote by at least 40% of all those eligible to do so if the strike involves “important public services”.

This is being fiercely opposed by trade unionists, who say it threatens their right to strike, but there are a number of subsidiary measures that are also causing alarm. These include the suggestion that unions will have to give two weeks’ notice to the police if they plan to campaign via social media.

A consultation document also suggests that approved picket supervisors would have to take “reasonable steps” to tell police the name, contact details and location of those on the picket line. Workers would also have to wear an armband or badge to identify themselves.

Speaking on Sky News’s Murnaghan programme on Sunday, Davis said: “I agree with most of the trade union bill. I think it’s very sensible … but there are bits of it which look OTT, like requiring pickets to give their names to the police force. What is this? This isn’t Franco’s Britain, this is Queen Elizabeth II’s Britain.”

The proposals have also been criticised by Liberty, Amnesty International and the British Institute of Human Rights.

The legislation will be debated in the Commons on Monday and will be strongly opposed by the Labour party and its new union-backed leader, Jeremy Corbyn.

In his victory speech on Saturday, Corbyn said he would fight the Conservatives’ attempt to “to shackle unions”.

However, the bill only has a chance of being challenged if more Conservatives, like Davis, object to restrictions on the grounds that they threaten civil liberties.