Britain’s biggest trade union will today mount a major push for Labour votes across some of the biggest cities in the north as it unveils a poster campaign to highlight the Tories’ shameful neglect of British industry.

Unite will warn that the Tories are “no friends of the north” as it reveals billboards in Leeds, Newcastle, Sunderland and Salford as well as dispatching advertising vans to tour London, the north east and north west.

The union, which is a major Labour donor and gave more than £2m to the party this month, will highlight real terms pay cuts under the Tories as well as its failure over the Redcar steel plant. Sajid Javid, then the business secretary, was widely criticised for being asleep at the wheel when the 98-year-old facility closed in 2015.

Today Len McCluskey, general secretary of Unite, will attack the Tories for presiding over falling pay and a chaotic Brexit while they directed help to the “leafy shires”.

“The Tories are not and never will be the friends of the North,” McCluskey is expected to say.

“When the Tories are in power, our great northern cities and communities endure misery and neglect. Just look at what happened to Redcar recently – a top class industrial facility was allowed to go to the wall by the Tory government with thousands put out of work.

“This is what a Conservative government does. It does not govern for the nation but rewards only the privileged, the leafy shires and the lucky few.

“That is why we are urging voters to think very carefully ahead of the poll on 8 June. Judge the Tories by their record – record debt, falling wages, appalling zero hours work, our children’s schools begging for help, police cuts, and our NHS on its knees. These leopards have not changed their spots and are not worthy of your vote.

“A vote for Labour is the only option to give our communities the strong future they deserve.”

McCluskey has been one of the biggest defenders of Jeremy Corbyn over the last 18 months. Earlier in May he appeared to cast doubt on the party’s prospects at the general election before saying journalists had taken his words out of context and declaring “there is everything to play for”.