Andy Burnham expected to say he will push ahead with electoral reform plans

Andy Burnham is expected to announce that he will push ahead with plans for electoral reform in his first conference speech as Labour leader, in the latest sign that he intends to radically transform the UK’s political system.

The prime minister, a longtime advocate of reform, will kick off a process that could eventually lead to ditching the first-past-the-post system in favour of proportional representation.

Government sources told the Guardian that Burnham would set out his plans in “broad strokes” in the speech, underlining his commitment to drawing up proposals before the next general election.

Along with social care changes and closer ties with the EU, the plans – which would represent the most significant shake-up of the electoral system since 1918 – would then be put in Labour’s manifesto to get public backing.

One option open to Burnham is to set up a new national commission for electoral reform, an idea he endorsed at last year’s party conference as Greater Manchester mayor.

At the time, he said there should be “a manifesto commitment to a system of proportional representation to be introduced into Westminster elections in the next parliament”.

Almost 100 Labour MPs supported the plan when the representation of the people bill went through parliament earlier this month. The minister leading the bill, Florence Eshalomi, told MPs that Burnham “remains committed to electoral reform”, while warning it was “premature to legislate now for one approach”.

Polling of MPs by YouGov suggests the change is supported by a majority in the Commons. Of those polled, 53% of MPs said they supported a review into first past the post.

In May, before he returned to parliament, Burnham told the Guardian that sweeping changes to the electoral system to make politics “less point-scoring, more problem-solving” would be needed if he becomes prime minister.

Critics of proportional representation have said it would lead to a more chaotic form of government, with unstable coalitions and an inability to pass legislation.

Yet Burnham has long argued that Britain has suffered from an overcentralised, London-centric form of government where two parties dominate at the expense of many of the UK’s nations and regions.