Paolo Nutini was too shy to ask Danielle Haim to feature on his new song 'Acid Eyes'.

The 'New Shoes' hitmaker has revealed the track on his comeback album, 'Last Night in the Bittersweet', was penned with the Haim star in mind, but his nerves got the better of him when it came to asking her to duet with him.

In a rare interview with The Sun newspaper, Paolo said: “I wrote that in my living room. I wanted to try and write a song that maybe Danielle from the Haim girls would sing with me. There’s the two vocals, the high and the low, which I figured was a duet. Everybody said why don’t I ask them to do it but I thought, ‘What if they say no?’. So I didn’t."

The 35-year-old Scot had previously met Danielle - who is joined by sisters Alana and Este in the pop trio - when her guitarist then-boyfriend Blake Mills was invited to work on Paolos last album, 2014's 'Caustic Love'.

He recalled: “I met them for the first time when we were making the 'Caustic Love' album. We worked with producer Dave Sardy, who brought in Blake Mills to play guitar. At the time his girlfriend was Danielle Haim and she swung by."

They also partied at Glastonbury in 2014.

Paolo said: “Then last time we played Glastonbury, Haim were backstage when we played The Other Stage and we ended up having a few drinks with them. They were really nice to me and my friends and they are great. And maybe if they hear of this?.?.?.?”

On his fear of rejection, he added: “Honestly, it’s a very human thing to feel anxious. I envy people who think they’ve got it all sussed and under control."

'Last Night in the Bittersweet' is out now.