Tory culture spokesman Peter Ainsworth said that any move to carry ads on BBC Online would hit at the heart of its public service remit and could sound the death-knell for the licence fee.

"There will be significant consequences for the licence fee. No one should be under any illusions," said Mr Ainsworth. "It will be hard for the BBC to justify its hefty licence fee if it starts taking ads on its public service website.

"It's yet another example of the BBC being an unchained beast marauding around the ecology of broadcasting."

Mr Ainsworth said his sources at the BBC suggested the issue of advertising on BBC Online had come out of conversations about moving some of the lifestyle-oriented content on BBC Online over to its commercial site, beeb.com.

This would put the gardening and food websites into the commercial domain and enable the BBC to start making money from the content.

He said he would welcome such a move, adding: "It would be better to move material over to where advertising already appears and give a better definition to BBC Online."