Worth $355 million, Rep. Darrell Issa is the richest member of Congress

Republican Darrell Issa of California was 2012's richest member of Congress, worth at least $355 million, according to a ranking published Tuesday.

The congressman, who made his fortune in car security systems, topped the annual list of the 50 wealthiest lawmakers published by The Hill newspaper, a trade publication about Washington politics.

A large portion of Issa's assets come from investment funds and properties valued in the millions.

The rankings were based on financial disclosure forms filed by members of Congress, which categorize the lawmakers by wealth range rather than an exact number.

Of the 50 richest members of Congress, 29 were Republicans. The US lower chamber fared better than the Senate, with 37 of Congress's most financially well-off coming from the House.

Lawmakers who are tipped as possible contenders for the White House in 2016 were scattered across the prosperity board.

Republican Congressman Paul Ryan of Wisconsin, who was Mitt Romney's running mate in the 2012 presidential elections, was worth at least $2.3 million. Republican Congressman Marco Rubio of Florida was worth around negative $190,000.

Issa has been a sharp critic of US President Barack Obama, chairing the House Oversight Committee, which among other duties, is tasked with monitoring the executive branch.

Outside of Congress, President Obama and his wife Michelle Obama were worth between $1.8 and $6.8 million in 2012 according to figures published in May.