It looks like Bono may have accidentally spilled the beans on his U2 bandmate Adam Clayton's baby news on-stage in London on Saturday.

The band were performing at London's Twickenham Stadium as part of their Joshua Tree Tour when he seemed to slip up and announce that the U2 bassist and his wife Mariana de Carvalho were expecting their first child.

Bono said to the crowd, "Is Adam Clayton not a sexy man?" to lots of cheering, before asking him, "Is your sexy woman here tonight?"

Clayton nodded, and Bono continued, "And expecting a baby, can I say that?" Clayton firmly shook his head and Bono said "Ok, can't say that" while waving his arm in the air.

Fans soon took to Twitter to share their surprise at Bono revealing the news.

U2 news account @atu2 also tweeted the news, saying they are "still gobsmacked" that Bono made the unexpected baby announcement.

The couple have not yet commented on the reports. 

The musician and Brazilian art gallery director tied the knot in 2013 after four years of dating.

Meanwhile, Adam recently thanked his U2 bandmates for their support in helping him overcome alcoholism.