The campaign, which was planned before the recent terrorist attack in Madrid earlier this month, shows pictures of people's eyes with the headline "Life Savers".
The ad warns that "Terrorists need places to live and to make plans... they need vehicles and people to help them. If you have any suspicions about terrorist activity... Don't hesitate." A telephone number is then given".
Posters have appeared on bus shelters and the ads have run in the Evening Standard and local newspapers. There is also a radio campaign.
Complainants have said that the eyes in the poster seem to represent a Muslim woman in a veil. The ASA is looking into the complaints.
The campaign features the eyes of an Asian-looking man and is highly reminiscent of the M&C Saatchi "demon eyes" poster that the Conservative Party used as part of its 1997 election campaign to attack Tony Blair.
The Tory campaign created a huge controversy at the time. The ad was condemned by the advertising watchdog the ASA and became a "political football" in the run-up to the general election, which led to a landslide Labour victory.
The Met ad was created through the Met's old agency The Advertising Syndicate, with media through Mediacom, although Miles Calcraft Brigginshaw Duffy has been retained on its £2m ad account. "Life Savers" is being run as a joint effort by the Met and City of London police.
Last month David Veness, Met assistant commissioner of specialist operations, said: "We want to make London one of the most hostile environments for anyone committed to providing financial or logistical support to terrorists, or carrying out terrorist attacks themselves."
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