They used to say revenge was best served cold. But that was before George Osborne discovered a better way – serving it regularly, in the pages of the newspaper he edits, to a captive audience of commuters.

The former chancellor was pointedly not invited to join Theresa May’s cabinet when she took over as prime minister, and is no longer a Conservative MP, giving him freedom to speak his mind on the current election campaign.

On Tuesday the London Evening Standard did just that, publishing a bitingly critical editorial that savaged May’s approach to Brexit and her election strategy to date.

It said the Tory campaign had “meandered from an abortive attempt to launch a personality cult around Mrs May to the self-inflicted wound of the most disastrous manifesto in recent history”.

The prime minister had been right to say Brexit was the overwhelmingly important issue facing Britain when she called the election, “although we suspect the allure of a potential landslide was the real reason”, it said.

But in her dealings with the EU to date, “we could not have got off to a worse start”, the paper argued, citing “high-handed British arrogance” as part of the problem.

While dismissive of “what passes for [Jeremy Corbyn’s] campaign strategy”, the leader said both main parties had failed to show that Britain was not turning its back on the world.

“We have had no answers from Labour or the Conservatives” the paper said, adding that both must now begin to “treat the public like grownups”.