The deal, announced in May, was billed as the largest in UK media history, locking Birds Eye Wall's, Lever Faberge, Unilever Cosmetics International and Unilever Bestfoods into a four-year agreement with ITV. In return, Unilever is expected to gain discounts of 25%. An announcement at the time by Unilever referred to a "deal rather than "deals", but said it had been signed with both Carlton Sales and Granada Enterprises.
The ITC is believed to be acting in response to an "expression of concern made by a rival broadcaster about the way in which the deal was done.
A source at one commercial broadcaster said the simultaneous announcement of the deal raised concerns that it could fall foul of ITC rules. They prevent joint selling of airtime by Carlton and Granada and ban deals requiring advertisers to commit a share of revenue to ITV.
All three parties, Granada Enterprises, Carlton Sales and Unilever's media agency Initiative Media, which brokered the agreement, insist there were two separate deals.
Granada Enterprises managing director Simon Pardon said: "Granada reached independent terms of business with Unilever, that have no impact on any money spent with Carlton."
The ITC, which under the 1996 Broadcast Act has powers to regulate competition in the TV market, has stressed it is not launching a formal investigation at this stage.
An ITC spokesman said: "We are just assessing the situation to see if it raises any concerns about fair and effective competition in the market." If problems are identified, the ITC can launch an official investigation.
Carlton sales director Gary Digby said the deal was no different from long-term deals done historically.