ALL-NIGHT running on the London Underground will not begin until Mayor Boris Johnson “rewards and respects” hard-working staff, unions said yesterday as negotiations over the service resumed.

The Night Tube’s planned September launch was called off after the capital’s transport network was paralysed twice in a month over the summer.

Tube workers are concerned at being forced to work countless night shifts with inadequate rewards and safeguards, saying they would cause huge disruption to family life.

Last week Mr Johnson said the service was not “absolutely critical” — rowing back on many previous statements.

Some suspect he is preparing for the possibility that the launch will not go ahead before he stands down at next spring’s mayoral election.

As bosses and unions returned to conciliation service Acas for talks yesterday, rail union TSSA general secretary Manuel Cortes called on Mr Johnson to intervene personally.

“I’m sorry for London Underground’s senior management, as Boris Johnson undermines them with these public changes of mind about whether the Night Tube is critical,” he said.

London Underground chief operating officer Steve Griffiths insisted: “We remain operationally ready to deliver the Night Tube and have hired 500 mostly part-time staff to run it.”

Rail union RMT said it was “looking to make significant progress on the outstanding pay and conditions issues that will take us towards a start date.

“RMT is committed to delivering a Night Tube service that works for Londoners and which properly rewards and respects the staff across the network who will be absolutely key to making it tick.

“Safety of both staff and passengers has to be right at the core of any agreement.”