About 22% of the population attended the Olympic torch relay.
And a further 9% plan to visit sites where the torch was paraded, VisitEngland said today.
The tourist body added that around 21% of the adult population intend to take at least one holiday or short break in the UK by the end of this month.
This tourism is likely to generate around £2.3 billion.
But VisitEngland said that around 22% of people are undecided about their summer holiday plans, with 39% of these worried about the financial situation and 28% concerned about the weather.
VisitEngland chief executive James Berresford said: "I'm delighted that more than 10 million people are planning to holiday at home this summer.
"If we convert even half of those who are undecided about taking a summer break in England, we could potentially contribute an additional £600 million to the UK economy."
VisitEngland is already looking forward to another big sporting event to be staged in the UK - the 2015 Rugby World Cup.
The Rugby League World Cup in is taking place in England next year, while England will also host the 2019 Cricket World Cup.
VisitEngland said today: "The impact of these events, particularly the Olympic and Paralympic Games, will benefit generations for years to come."
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