Citing examples of various foreign companies, including at least one from India, a top American Senator has sought federal investigation into the alleged misuse of tourist visa to bring in foreign workers into the US.

"Given the problem such fraud and abuse in the B visa programme poses for American workers as well as the foreign workers who are mistreated and underpaid, I request that the departments respond to the concerns," Senate Judiciary Committee Chairman Chuck Grassley asked in a letter to the US Attorney General Loretta E Lynch.

In the letter which was also sent to the secretaries of the Departments of State, Homeland Security and Labour, the Senator sought more information on the types of visas granted to the workers.

He asked about a practice by the State Department that allows B visa holders to work in the US as if they had been granted H-1B skilled labour visas, and is seeking the legal justification for such a practice.

B visa holders are not granted the same worker protections that are required of companies employing H-1B visa holders.

"The manner in which the B visa programme is being used and the absence of real oversight and enforcement is a shame. Despite a long and undeniable history of abuse of the programme to bring foreign workers into the United States under cover as 'business visitors,' regulations and field governance governing the programme have not been updated in years," Grassley said in the letter.

In his letter, Grassley said that in October 2013, the Department of Homeland Security, Department of State, and United States Attorney's Office for the Eastern District of Texas entered into a settlement agreement with Infosys, as part of which the US government alleged that Infosys knowingly and unlawfully used B-1 visa holders to perform skilled labour in order to fill positions in the US for employment that would otherwise be performed by American citizens or require legitimate H-1B visa holders, for the purposes of increasing profits, minimising costs of securing visas, increasing flexibility of employee movement, obtaining an unfair advantage over competitors, and avoiding tax liabilities.

Infosys paid a settlement amount of USD 34 million, the largest payment ever levied in an immigration case. "And now the ongoing abuse of the B visa category is once again at the centre of scandals attracting widespread press and social media coverage," he said.

"It's also obvious that investigation of B visa abuses and unauthorised employment of B visa holders is a rock-bottom priority for all of your Departments - with the exception of the Department of Labour, which has been doing some good work in uncovering these abuses," Grassley said.