Ministers are preparing to back down over new trade union laws over fears parts of the bill will be defeated in the House of Lords

The proposed concessions have emerged in a letter leaked to Socialist Worker, which reveals business minister Nick Boles is recommending a retreat from some controversial measures in the bill.

The letter, sent to fellow ministers, proposes extending the four-month time limit on the validity of a ballot to six months and scrapping the need for picket supervisors to wear arm bands.

Labour, the Liberal Democrats and some crossbench peers have been preparing to fight some measures in the trade union bill in the House of Lords this week.

In the letter, marked official and sensitive, Boles said parts of the bill were facing defeat in the second chamber and suggested the government should pick its battles.

He indicated “a willingness to give some ground on certain aspects of the bill may lead to a less hard line response to the bill on other issues”.

Nick Boles Photograph: Rex Features

The suggested concessions include:

A review into whether unions should be allowed to conduct e-ballots for strikes. This is needed because “the threshold provisions [the flagship element of the bill] will be defeated if we do not make some move towards accepting the possibility of electronic balloting”.

Setting up a procedure to consult the Scottish parliament and Welsh assembly on the bill. In addition, Boles suggests the government may have to retreat further in Scotland and Wales.

Withdrawing the increase in the notice period for industrial action from seven to 14 days.

Increasing the time that a ballot is legally valid from four months to six months.

Deleting the need for a picket supervisor to wear an armband and badge.

In response, Frances O’Grady, the general secretary of the Trades Union Congress, said: “The changes discussed in this correspondence are important. However, they do not go far enough. While ministers are right to call for check-off arrangements to remain in Scotland and Wales, they are still planning on banning public sector employers in England from deducting union subs via payroll.

“And holding a review into electronic balloting without an end date is simply not good enough. If online balloting is safe and secure enough for the Conservatives to select their candidate for London mayor, there can be no excuse for delaying its introduction for union members.”

Trades Union Congress general secretary Frances O’Grady said the proposed changes need to go further. Photograph: Stefan Wermuth/Reuters

Lorely Burt, Lib Dem peer and business spokeswoman, said: “We are pleased that the government apparently recognises the need to allow electronic balloting of trade union members if they want to impose voting thresholds on unions. We hope they will therefore listen to Liberal Democrats who have tabled amendments to the trade union bill to allow electronic voting.

“This leaked letter shows just some of the problems with this politically motived attack on trade unions. This is not about good industrial relations, it is about attacking one of their political opponents.”

A spokeswoman for the Department for Business, Innovation and Skills said: “We do not comment on leaks. The government is committed to implementing the trade union bill and to balancing the right to strike with the right of millions of people to go about their daily lives.”