An aide to Labour's London Mayor candidate Sadiq Khan quit today after a series of damaging revelations emerged, including pictures of him brandishing a gun and boasting that he could be hired as a 'hitman'.

Shueb Salar also claimed that Fusilier Lee Rigby's killing was faked, posted a series of sexist, racist and homophobic comments on Twitter and joked about rape and murder online.

The revelations raised questions about Sadiq Khan's judgement in hiring Mr Salar despite the offensive posts having been posted long before Mr Khan employed him as a speechwriter in November 2014.

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Shueb Salar posted pictures of himself posing with a gun and posted online that he could be 'hired as a hitman'

Mr Salar continued to post the controversial comments while working for Mr Khan in Parliament.

The aide resigned this morning as more revelations emerged, with pictures showing him brandishing a gun alongside comments claiming he could be hired as a 'hitman'.

He posted a video of himself online posing with a rifle and explaining how he had spent the weekend 'shooting stuff with real guns, knives, crossbows and bow and arrow's', according to the Standard.

Alongside the picture he added the Twitter hashtags: '#I'mASecretHitman' and 'ShoutMeIfYouWantMeToTakeCareOfSomeone and '#I'llMakeItLookLikeAnAccident'.

Shueb Salar, pictured left posing with a gun and pictured right alongside Sadiq Khan, Labour's candidate for London Mayor, resigned after new pictures of him emerged today

Along with homophobic and sexist comments, Mr Salar joked about rape and murder, claims Bengali people 'smell' and said he thought the slaying of soldier Mr Rigby by extremists in 2013 may have been fabricated.

Yesterday a spokesman for Mr Khan, who is the current favourite to beat Conservative Zac Goldsmith to succeed Boris Johnson as Mayor of London, said Salar had been suspended pending an investigation.

But the Tory Leader of the House of Commons Chris Grayling said the revelations raised questions about the suitability of Mr Khan for running London.

'The real issue here is about Sadiq Khan's lack of judgement,' he said. 'If he really is surrounding himself with someone so unfit to be playing a role in public life then you have to ask whether he himself is fit to be Mayor of London. Trivialising violence can never be justified.'

And Essex MP and Employment minister Priti Patel questioned how Mr Salar had made it through the vetting procedure in the first place.

Shueb Salar quit after new pictures emerged of him posing with a shotgun and boasting that he could be hired as a 'hitman' and saying he would 'make it look like an accident'

MP Priti Patel, pictured, called for Salar to be sacked in a letter, saying: 'Why not dismiss him immediately?'

In a letter last night calling for the aide to be sacked, she wrote: 'Why not dismiss him immediately? By deciding to only suspend him, you are in effect suggesting that the offensiveness of these views are open to interpretation.'

A 2013 post by Salar the day after Mr Rigby was brutally hacked to death in the street in south-east London says: 'I had the feeling the Woolwich killing was probably fake.'

It was followed by a link to a YouTube clip that has footage of killers Michael Adebolajo and Michael Adebowale at the murder scene with commentaries questioning whether it was a hoax.

Salar's anti-gay tweets include one which he said two men who were harassed for kissing on the Tube may have 'deserved it'.

Others read: 'Currently hating all you faggots who have finished uni'. Referring to women as 'hoes' [whores] or 'bitches', he says 'treating a lady' means 'buying her a nice iron and extending the kitchen'.

Pictured are a selection of tweets that Salar posted between 2012 and 2013, in which he makes sexist comments and says that he thought the killing of soldier Lee Rigby was 'probably fake'

Reversing the rags to riches tale of Cinderella would be 'the story of a woman learning her place', he added.

The sexist comments are particularly embarrassing as Mr Khan yesterday attended a special £30-a-head screening in London of the 2015 movie Suffragette, with all proceeds going 'towards winning London for Labour in May'.

The event was billed as celebrating Mother's Day and International Women's Day with the comment 'women's equality is good for all'.

Mr Khan gave a short speech in which he described himself as a 'feminist' and said Labour would stand up for women's rights.

Here is a list of the offensive posts tweeted by Shueb Salar, which included sexist and homophobic messages

However, Tory politicians expressed incredulity at Mr Khan's failure to vet an employee with such vile opinions.

Former police and criminal justice minister Damian Green said the mayoral candidate had shown a 'completely extraordinary lack of care'.

'I can't believe that he would have known that he had said any of this stuff, so I can only assume he didn't check anything about him before,' he added.

Kingston and Surbiton MP James Berry said: 'The most elementary of background checks would have revealed these messages.'

Leader of the Commons Chris Grayling told the Mail on Sunday: 'They raise serious questions about the judgment of Sadiq Khan, who chose to employ this man, despite his views being public, on a Twitter account followed by Khan himself.'

Salar, 24, an amateur boxer who previously worked for a solicitor's firm specialising in human rights, has moderated his comments since starting to work for Mr Khan.

But he continued marking other people's tasteless comments as 'favourites'. His Twitter account has now been shut down.