THE Federal Government's travel advisory to Britain is inadequate and underestimates the extent of the terrorism threat there, tourism figures and security experts have warned.

London is now seen as the prime western target for jihadists, especially after Britain's spy chief revealed there were 30 active terrorist plots and 1600 suspects.

More than 900,000 Australians travel to Britain each year, and hundreds of thousands more live there.

The Department of Foreign Affairs and Trade tells travellers only to exercise caution and monitor developments. On the department's scale of one to five, Britain is judged in the second lowest category of risk.

Indonesia, by contrast, is in the second highest category, below only a few countries such as Iraq, Afghanistan and Sudan.

"The industry is concerned that, given the number of things that have happened in the UK, given they have been happening at an increasing rate, that the travel advisory is inadequate," said one senior tourism industry figure. "We would say - on the information we have - there is more likely to be an attack in London than Jakarta … or even Bali."

Indonesia's security agencies are on high alert for the visit of the United States President, George Bush, today. But while the threat from Islamic extremism remains in Indonesia, the country has not suffered a large-scale terrorist attack in the past 12 months, the first time for more than five years.

As well as coping with the bombings by Islamic extremists on London's underground rail and bus system in July last year, British authorities this year said they had narrowly thwarted a plot to blow up as many as 10 planes leaving the capital's Heathrow Airport.

"The situation in the UK is not good and there very much remains an ongoing potential for attacks," said Clive Williams, adjunct professor at Macquarie University's centre for policing intelligence and counter-terrorism. "People who are travelling there should be concerned."

As a prominent member of the coalition that invaded Iraq, Britain has become the prime target in the West for violent Islamic extremists.

There was a large population of disaffected Muslims and Islamic radicals after Britain's intelligence services turned a blind eye to their activities in the 1990s, Professor Williams said.

They wrongly assumed the militants wanted to hit targets only in the Middle East. "They are now playing catch-up."