Amir Khan is ready to do the unpalatable: swallow his pride and fight on Floyd Mayweather's undercard to earn a shot at the American's world welterweight title later in the year. And he is so angry he promises to retire Mayweather's friend, Adrien Broner, if he gets the chance.

The Bolton boxer reckons Mayweather duped him into believing he would be his next opponent on 3 May, then used what he regards as a dubious fans' poll to opt for Marcos Maidana, whom Khan had already beaten.

Mayweather is a predictably strong favourite to retain his title and flawless record by beating Maidana, and this week said Khan would get his chance to spoil his career in September – if he fought Broner. "If Broner wants to fight me I'm ready," a plainly frustrated Khan tweeted. "Please can you get your legal team to reply to my team!"

He went on: "Broner, you didn't even give an interview after your last fight [a one-sided beating by Maidana]. Instead you cried your way out of the ring like a baby." He added: "Broner should keep quiet. [Paulie] Malignaggi beat him but didn't get it. Maidana the fight after destroyed him and I would make him retire."

Khan broke training and returned to the UK from the US on Wednesday to spend a few weeks with his family. He seems resigned to accepting the consolation fight against Broner and says he will make an announcement next week.

Khan still insists Mayweather had promised to fight him next – through his American partners, Golden Boy Promotions – which is why he declined a December fight against Devon Alexander, who then lost his version of the 10st 7lb title to Shawn Porter.

Khan is not one of boxing's renowned trash talkers, so it was surprising that he directed a personal insult at Broner, who has a reputation for uncompromising exchanges: "Just got told Broner doesn't run his Twitter page. He can't read or write. It's probably one of his stripper girls hyping it for him."

Without a title to parlay, Khan's bargaining power is diluted. The Matchroom promoter Eddie Hearn last week offered him $5m to fight Sheffield's unbeaten Kell Brook but he did not respond. Brook is the mandatory challenger for Porter's welterweight title – the one Khan might own had he not put his trust in Mayweather and Golden Boy.

Brook ticks over against Mexican puncher Álvaro Robles on 15 March, comfortable in the knowledge that Porter has to start negotiations by 7 April, although the American could still squeeze in a voluntary defence of his IBF title before then.

Former gym-mates Anthony Crolla and John Murray will meet at the Phones 4U Arena on 19 April in a 12-rounder that could lead to a world title challenge. It looks as if the Mancunians are edging ahead of Glasgow's champion Ricky Burns, who lost his world lightweight title to the American Terence Crawford on Saturday night.

Murray, who fell out with Crolla's trainer Joe Gallagher, lost to Brandon Ríos in a challenge for his world title in 2011, and, in only his second fight since, stepped in for the injured Crolla on the Burns undercard to stop Scot John Simpson in two rounds.

Crolla, coming off good wins against Gavin Rees and Stephen Foster, has a WBO Inter-continental title to use as a lever towards a world title.

"This is the one that I have always wanted," Murray said on Wednesday. "I hope that in the buildup people concentrate on us and not Joe Gallagher, we're doing the fighting. This is the reason I turned pro, I wanted to be on big bills in Manchester – Anthony and I are friends but we won't be until after the fight."