The troubled broadcaster is among several companies in the relegation zone ahead of the cut-off point at Tuesday's close for the quarterly reshuffle of the London Stock Exchange, which will kick in on September 22.
At 2.30pm today, shares in ITV were trading at 44.6p -- down from a year high of 112.7p.
The current price gives the company a market capitalisation of £1.73bn, down from £4.4bn last September.
Last month, ITV announced pre-tax profits in the six months to the end of July were down 28% year on year to £91m.
It also warned that it expected TV ad revenues in September to be down 20% on the same period last year.
The broadcaster's relegation from the FTSE 100 would leave just five media companies in the top league of Britain's biggest public firms.
The biggest is currently BSkyB, with a market capitalisation of around £8.3bn.
Reed Elsevier, which has invited bids for its business publishing arm, comes second on £6.7bn, closely followed by global advertising giant, WPP on £6.3bn.
Financial Times publisher Pearson (£5.6bn) and recently merged news agency Thomson Reuters (£2.8bn) are also included in the list.