Amazon workers will stage the first-ever UK strike against the online giant on Wednesday in a protest over pay.

Members of the GMB union are walking out at Amazon's Coventry warehouse over what they call a "derisory" 50p an hour pay rise.

Workers told the BBC about "severe" conditions, claiming they are constantly monitored and upbraided for "idle time" lasting just a few minutes.

Amazon said it has a system "that recognises great performance".

A spokesman said it "also encourages coaching to help employees improve if they are not meeting their performance goals".

But two Amazon workers, who are members of the GMB, said the robots in the warehouse "are treated better than us".

Darren Westwood and Garfield Hilton described to the BBC how even a trip to the toilet can lead to questions by managers.

"The thing is with stopping work is that they want to know why," said Mr Hilton. "So if the time is beyond a couple of minutes they can see it on the system."

Mr Hilton, who has diabetes, said it is not always possible to find toilets close by in the building and the process of locating one and returning can sometimes take upwards of 15 minutes.

"They will then question you "what were you doing?'."

They said that managers track staff performance and time that is not spent scanning items is accrued.

Workers at the Coventry warehouse scan stock which is sent out to Amazon fulfilment centres, to be shipped to consumers.