A campaign has been launched by police and travel organisations to reduce travel fraud in relation to Hajj.
Around 25,000 British Muslims make the pilgrimage to Mecca, the birthplace of Islam, in Saudi Arabia each year and many will book their travel arrangements over the coming weeks.
Many victims who do not receive the flight tickets or accommodation they pay for are either too embarrassed or frightened to report what has happened to them, according to law enforcement and Muslim community leaders.
City of London Police will visit Heathrow, Gatwick, Stansted and Birmingham airports to raise awareness of the issue and give briefings at mosques.
The campaign is supported by the British Council of Hajjis (CBHUK), travel association Abta and Atol, a financial protection scheme from the Civil Aviation Authority.
City of London Police Commander Dave Clark said: "Many people save for years to be able to afford a once-in-a-lifetime pilgrimage to Mecca.
"Unfortunately, fraudsters often prey on unsuspecting citizens, leaving families with no flights or accommodation for the trip.
"We are therefore urging people to research their Hajj plans thoroughly and take care to check authenticity of the offer and agents offering their services. If it's too good to be true, it often is."
People booking package trips with flights for Hajj this autumn are advised to make sure the company is covered by the Atol scheme to offer protection against losses if it goes out of business.
They are also warned against paying by cash or direct bank transfer, and it is suggested they obtain all booking confirmations in writing.
Mark Rayner, Atol's head of compliance, said: "It is really important that anyone looking to travel to Mecca this September, as part of a Hajj pilgrimage, to look beyond the price and check, then double check that the travel business has Atol protection and ensure they receive an Arol certificate once they pay any money towards their trip."
CBHUK chief executive Rashid Mogradia said: "The community needs to play its part and report fraudsters who dupe people out of thousands of pounds and shatter their dreams of fulfilling the journey of faith - the Hajj."