Andy Burnham has snubbed a desperate bid by Keir Starmer to buy him off with a Cabinet job.The PM praised Mr Burnham as a 'fantastic asset' and said he wanted him to have a 'big role' in Government if he wins the Makerfield by-election tomorrow.Sir Keir also attempted to delay the prospect of a leadership challenge, suggesting Labour would need to focus on a contest to replace Mr Burnham as Greater Manchester mayor. That could potentially take until August.However, a source close to Mr Burnham dismissed the idea he could join the premier's team, insisting he was gaining support because he represents 'change'.Despite vowing he will not walk away Sir Keir - who is in France for the G7 summit - is facing an increasing clamour for change at the top of the party. There are claims that Ed Miliband is ready to resign next week to force Sir Keir out if he refuses to go quietly.The Net Zero Secretary has been tipped to join allies of Mr Burnham in walking out of Government.Wes Streeting has said he will mount a formal challenge if Sir Keir does not quit voluntarily by Monday, regardless of the by-election result. Keir Starmer praised Andy Burnham as a 'fantastic asset' and said he wanted him to have a 'big role' in Government if he wins the Makerfield by-election tomorrow Mr Burnham is expected to mount a challenge swiftly if he succeeds in making a return to the House of Commons