British rocker Ian Watkins of the band Lostprophets on Wednesday failed in his bid to reduce his 35-year jail sentence for a string of child sex crimes including the attempted rape of a baby.

Court of Appeal judges in Cardiff told the 37-year-old singer they would not grant leave for appeal.

"These offences against children were of shocking depravity... a very lengthy prison sentence was demanded," said Christopher Pitchford, one of the judges considering the bid.

Last year, judge John Royce handed Watkins a 29-year jail term as well as an additional six years on licence after he admitted 13 offences, saying he had "plumbed new depths of depravity".

One of Watkins  two female accomplices also had her appeal bid turned down.

The singer, whose now-defunct band sold millions of albums around the world, plotted the abuse of two children with their own mothers in a series of text and Internet messages.

After sexually touching one groupie s 11-month-old baby son, the heavily-tattooed rocker then tried to have penetrative sex with the child.

He also encouraged a second fan to abuse her female child during a webcam chat and secretly stashed child porn videos, some of which he had made himself.