John McDonnell today laid out the basis of Labour’s critique of Theresa May by attacking her “reactionary” new Cabinet and warning it could undermine workers’ rights yet further.

The shadow Chancellor said the fresh Government line-up would deliver “neoliberal” policies and threaten the existence of trade unions.

McDonnell, who was speaking at Unite’s policy conference in Brighton, also ridiculed May’s Cabinet appointments as she put the finishing touches to her senior team, which include moving Philip Hammond to the Treasury and promoting Boris Johnson to Foreign Secretary.

“Yesterday we heard Theresa May’s first speech as prime minister…. Just remember she has voted for every cut in welfare spending, every cut in working families tax credits, every cut in social care… every cut that has resulted in Foodbank Britain,” McDonnell said.

“Now she has appointed a neoliberal hawk to the Treasury and a graduate of the Donald Trump school of diplomacy to the Foreign Office.

“She is establishing a right wing reactionary cabinet which will drive through right-wing neoliberal policies… and will undermine the very existence of those organisations which stand up for working people.”

McDonnell said the Government had led an “onslaught” on trade unionism since 2010 and re-committed Labour to repealing the Trade Union Act.

He also mounted a defence of his economic policy since he and Jeremy Corbyn rose to the top of the party in September last year. The pair have positioned Labour as a fiercely anti-austerity party whereas under Ed Miliband and Ed Balls the frontbench accepted the need for some spending cuts as part of plans to cut the deficit.

McDonnell said his project with Corbyn was to transform society so “prosperity is shared for all”.

“My job as shadow Chancellor is to tackle that one key issue that, to be frank, lost us two key elections, that is restoring economic credibility to the Labour Party.

“Our ambition was to raise the level of economic debate in this country – going beyond the inane debate of [George] Osborne which reduced the economic debate to platitudes.”

Several former shadow Cabinet members from the Miliband era fear that McDonnell’s stark anti-austerity position will not be accepted by a public which last year returned the Tories to power on the back of pledges to eliminate the deficit.