ITV has failed to meet quotas for the number of programmes it makes outside London, Ofcom has said.
ITV1 should have spent at least 50 per cent of its production budget on programmes made outside the M25, but fell "significantly below" that at 44 per cent last year, the communications regulator said.
A separate audit revealed ITV1 also failed to meet the quota during 2006, spending 46 per cent on programmes outside London.
Ofcom said it was taking the issue "very seriously".
It said in a statement: "Ofcom believes it is important that broadcasters meet the minimum requirements set out in their licences.
"ITV’s failure to meet the value element of its out-of-London quota is a serious matter, and one which is the subject of further consideration by Ofcom with a view to regulatory action."
The Communications Act requires networks to spend a set amount of their production budget outside London.
The quota applies to all network programming including dramas and comedies but excluding news.
It is thought to be the first time a network has fallen short of the quotas.
Ofcom said the BBC spent three per cent more than its quota in 2007, Channel 4 spent five per cent more and Five extended its quota by three per cent.
The failure could mean more fines for ITV1 following a series of premium rate phone-in scandals.
Earlier this month Ofcom imposed a record £5.67 million fine on ITV, accusing it of "institutional failure" and programme makers of a "total disregard" for broadcasting rules.
Ofcom chief executive Ed Richards said then that ITV bosses "may well" face a police investigation, and it was for the the Serious Fraud Office to decide if criminal action was appropriate.
It also emerged this month that organisers of ITV’s 2005 British Comedy Awards promised pop star Robbie Williams he could present an award to Ant and Dec even though the actual winner should have been The Catherine Tate Show.
An investigation revealed viewers of the show were asked to keep voting on premium rate lines even though the duo had already been filmed winning the People’s Choice Award.
ITV said in a statement: "ITV did meet the required volume of out-of-London productions in 2007. However, we accept that the quota in terms of value was not achieved during this period.
"We recognise that we must comply with these challenging obligations and we will be taking the necessary steps to meet the quota in 2008.
"ITV is committed to a diversity of production and set up the Nations and Regions Production Fund in 2005 to encourage commissions from producers based outside of London."