Morrisons has had a tough ride since taking over Safeway

Morrisons admitted that a thorough review of its depots was under way, but the union says staff were not consulted and is now threatening strike action.

The depots involved, in Kent, Bristol and Cheshire, were formerly owned by Safeway which Morrisons bought in 2003.

Morrisons has seen profit alerts and a falling share price since the buy-out.

The GMB said there had been no consultation between it and Morrisons about redeploying workers.

Morrisons has run a coach and horses through its legal obligations Jude Brimble, GMB union

It also said it had no idea whether the sites were going to be sold as a going concern or closed down and "bulldozed and all the rest of it".

Jude Brimble, national officer for the GMB, told the BBC: "These are all long-serving Safeway employees in these depots - a couple of thousand workers."

Strike warning

Now the union has warned that Morrisons could face the biggest national strike in its history.

"Morrisons has run a coach and horses through its legal obligations to consult with the workforce and unions prior to drawing up plans which will lead to large scale redundancies," Ms Brimble said.

In response, Morrisons said it had already made it clear that a wide-reaching review of its depot operations was taking place.

"Since acquiring Safeway, we have sold over 180 stores and the reality is that we have more depot space and capacity than we need," the supermarket group said in a statement.

"Therefore it is likely that not all current operations will be retained once our review is complete."