Ticketing has been the most contentious issue for London organisers in the run-up to the July 27-August 12 Games.
Demand for many events has outstripped supply, prompting complaints about the way tickets were allocated, the cost and technical glitches in handling applications.
Anger was fuelled at the weekend when the Sunday Times reported that National Olympic Committees and Authorised Ticket Resellers representing 54 nations had broken rules over the sale of London 2012 tickets.
With Olympic tickets now being delivered to British homes, police are stepping up efforts to halt black market trade, also known as ticket touting
"At this time when the majority of tickets have been sold, the public need to be more wary than ever about buying from an unauthorised source," said Detective Superintendent Nick Downing.
"If they are tempted to do so, they run the risk of being ripped off for non-existent tickets or having their personal details stolen and used in other crimes," added Downing, head of the "Operation Podium" drive to stamp out illegal sales.
British police said they had disabled two websites in a joint investigation with Portuguese colleagues and had charged a 44-year-old man with fraud and money laundering.
Sales for the latest batch of Olympic tickets had been unusually sluggish, prompting talk of "ticket fatigue" among cash-strapped Britons.
Prestige Ticketing, an authorised Olympic partner, has taken out newspaper advertisements for its remaining VIP ticket, food and drink hospitality packages, usually the preserve of corporate customers.
However, the prices start from £695 per person for athletics in the Olympic Stadium, putting them out of the reach of many potential customers.
Meanwhile, the International Olympic Committee asked Sochi 2014 Winter Games organisers to delay their international ticket planning in order to review the situation after alleged breaches in the London 2012 sales.
"Following the recent Sunday Times allegations that some national Olympic committees and authorised ticket resellers were in breach of 2012 Games ticketing policy, the IOC has convened its Ethics Commission to undertake a comprehensive analysis of the story," the IOC said.
"During this process we have asked the Sochi organising committee to temporarily delay the planning for its international ticketing programme while we review the situation."
The newspaper had said numerous NOCs and ATRs were offering to buy or sell tickets outside their territories, to sell tickets at inflated prices or sell them to unauthorised resellers."
"The move is purely precautionary. Sochi 2014 is not affected by the allegations and we continue to work closely with them, as they develop their ticketing programme for the Olympic Winter Games."