The government has laid out its final plans for redrawing House of Commons constituency boundaries under a new system that probably would have turned the hung parliament of the 2017 election into a safe Conservative majority, prompting claims from Labour of an “undemocratic power grab”.

The plans from the separate boundary commissions for England, Scotland, Wales and Northern Ireland are the product of long and complex consultations that began in 2016 leading up to Monday’s publication.

Under the proposals, the number of Commons seats would be reduced from 650 to 600 and the maps of many constituencies redrawn in an attempt to even up population levels.

But as anger mounted on Monday among backbench Tory MPs whose seats would be at risk, there were suggestions that Theresa May would set the changes aside until next year.

Despite the broader advantage to the Conservatives, prominent pro-Brexit MPs including Boris Johnson and David Davis could find their seats under threat from the changes, which has led to fears that the vote could become another flashpoint in the party’s damaging split.

With the prime minister’s spokesman refusing to commit to a vote on the changes before Christmas, Chloe Smith, the minister for the constitution, said that drawing up the necessary plans would be a “complex and lengthy” process that would take “months to prepare”.

Among the changes confirmed are the disappearance of Jeremy Corbyn’s Islington North seat, which would be absorbed into a new area taking in part of the current constituency of Diane Abbott, the shadow home secretary.

The constituency of Haltemprice and Howden, represented by Davis, the former Brexit secretary, would also vanish.

The former foreign secretary Boris Johnson could face a tough battle to keep his Uxbridge and South Ruislip constituency, where he has a 5,000 majority, with a Conservative-leaning district to be replaced by a strongly Labour area.

The number of English seats would be reduced from 533 to 510, Scotland’s count would fall from 59 to 53, Wales would drop from 40 to 29 and Northern Ireland would lose one of its 19 seats.

In a written statement to parliament, the Cabinet Office minister, David Lidington, welcomed the final reports, saying the changes had been made in an “independent and impartial” way. He said adoption of the changes would need the approval of the Commons and Lords, and he gave no details of when this would happen.

Labour has condemned the plans as short-sighted, given the need to scrutinise Brexit, and pointed out that studies indicate the new system would have favoured the Conservatives in last year’s election.

One study by Colin Rallings and Michael Thrasher, academics at the University of Plymouth, calculated that the new boundaries would have given the Conservatives an overall majority of 16 in last year’s election. The Tories would have taken 10 fewer seats than they did and Labour 30 fewer.

The shadow Cabinet Office minister Cat Smith said the final recommendations amounted to “an undemocratic power grab”. “With no plans to reduce the number of ministers, the government is weakening the role of parliament and creating unprecedented levels of executive dominance at the expense of backbenchers, when parliament is meant to be taking back control,” she said.

“Cutting the number of MPs by 50 as we prepare to leave the European Union is further proof this government is clamouring to tighten its grip on power. With the workload of MPs set to rise after Brexit, with thousands of pieces of important legislation expected to come through parliament, it would be utterly ludicrous to go ahead with these boundary changes.”

The Boundary Commission for England said its final report took account of more than 35,000 comments from the public. Sam Hartley, the secretary to the commission, said: “We’re confident that the map we propose today is the best match of the legal rules parliament has set us. It’s now up to parliament to decide whether these boundaries will be used at the next general election.”

With Labour fiercely opposing the idea, and some Conservatives possibly rebelling, it is by no means certain the proposed system will be put into effect.

The plan was also condemned by the Electoral Reform Society, which said that if the number of ministers remained unchanged it would mean 23% of all MPs and 45% of Conservative MPs being obliged to vote with the government – an historic high.

The society said changes to equalise constituencies were tinkering when the first-past-the-post electoral system meant the number of votes per MP elected in 2017 varied from just under 28,000 for the Democratic Unionist party to more than 500,000 for the Green party.

The review was ordered in 2011 under David Cameron’s government with the stated aim of reducing by 50 the number of Commons seats and creating constituencies of roughly equal populations. They currently vary in England from about 55,000 to 95,000 voters.