Andy Burnham has demanded Theresa May give Britain’s regions a voice in Brexit talks rather than taking decisions through a “secretive” clique.

The Manchester mayoral candidate warned that delivering Brexit through the “London-leaning” view that has dominated politics for 30 years could fuel resentment which leads to the break of Britain.

Burnham used his first speech since stepping down from the shadow Cabinet to deliver a blunt verdict on the efforts so far of May, who he shadowed when she was Home Secretary. He also tried to steer the Government away from a Hard Brexit, which would be expected to mean leaving the single market.

“One of the great dangers facing the country right now is that Theresa May’s Government will create closed Brexit talks dominated by the same London-leaning perspective that has shaped national policy for 30 years and has failed to provide meaningful answers to former industrial communities. If the Government fails to give the nations and regions a seat at the table, it could fuel real resentment and be a short-cut to the break-up of the UK.

“In its response to Brexit to date, the Government has reverted to a discredited style of politics that lies behind the referendum result – a highly-centralised and secretive approach, with a closed clique calling all the shots and which shuts out other voices including Parliament.

“Theresa May has got the Brexit negotiations off on entirely the wrong foot and needs to change direction. She is working on the assumption that the country voted for a hard, confrontational Brexit when there is no evidence to support this. In fact, it would seem that the opposite is true – a majority of people were against a hard Brexit.”

Burnham was speaking at a New Economics Foundation conference in London at which his former shadow Cabinet colleague Ed Miliband revealed he had held private discussions with Sir Vince Cable when the latter was Business Secretary between 2010 and 2015.

Burnham has called on May to set up a Brexit committee of the nations and regions, including elected mayors, and to allow extra Parliamentary scrutiny of the talks leading up to the departure from the EU.

“Devolution in England was never conceived as part of the answer to Brexit but now it must be fully embraced as such,” he said.

“Brexit will have a differential impact on different parts of the country and a hard Brexit would hit the poorest areas hardest of all. Great effort will be expended to protect the financial sector and the City of London, which, while understandable, could lead to trade-offs that will damage other sectors…

“The aim of that committee should be to seek a fair Brexit that balances the needs of all parts of the country. It is essential that Greater Manchester has a place at this table.”