Downing Street has defended proposals to make visitors to pay a £3,000 security bond to enter the UK after the plan was condemned as "highly discriminatory" by Indian business leaders.

The scheme, which is due to be piloted from November, is aimed at deterring temporary visitors from "high risk" countries from staying on in the UK after their visas expire.

Although details are yet to be announced, it is been suggested that visitors from India, Pakistan, Sri Lanka, Bangladesh, Ghana and Nigeria will be required to pay a £3,000 deposit for a six-month visa, which will be forfeit if they do not leave when they should.

It is part of the Government's drive to cut net migration into the UK to the "tens of thousands" by the time of the next general election in 2015.

However, the Confederation of Indian Industry (CII) today denounced the plan as "highly discriminatory and very unfortunate", warning that it could delay agreement on an EU-India trade deal.

"The suggested changes are not only discriminatory they are also against the 'special relationship' publicised by the UK government. We share UK's concern on illegal immigration but surely there are other more effective and non-discriminatory ways to put a check on it," it said in a statement.

"The industry in India is disappointed by the way the immigration rules in the UK have been changing over the last few years.

"CII strongly feels that such blanket rules for visas will negatively affect not only businesses, especially small businesses, it will also further bring down the number of students going to UK for higher studies and affect the tourism inflow from India to UK."

Their complaints were echoed by the chairman of the Commons Home Affairs Committee, Labour MP Keith Vaz, who described the scheme as "unfair and discriminatory".

"This flies in the face of the Prime Minister's intention to attract the brightest and best to Britain and sends out the wrong message to the countries concerned. I am worried that the plans could potentially alienate already settled communities in the UK," he said.

Downing Street however insisted that the Government was determined to consider "all necessary measures" to bring down net migration.

Officials insisted that no decisions had been taken on which countries would be covered by the scheme and that work was on-going to ensure it was targeted at the highest risk cases.

"The Prime Minister is determined to cut net migration to the tens of thousands. The Government will continue to look at all necessary measures," a No 10 spokesman said.

"As part of this, the Government will pilot the role migrant bonds can play in deterring individuals that pose the highest risk of overstaying.

"But this will not stop business people or genuine students. Because we want to attract the brightest and the best to help create the jobs and growth that will enable Britain to compete in the global race."