The US Securities and Exchange Commission has sued Volkswagen and its former chief executive Martin Winterkorn over the German automaker's diesel emissions scandal.

The SEC has accused the German company of perpetrating a "massive fraud" on US investors. 

The SEC said in its civil complaint filed in San Francisco last night that from April 2014 to May 2015, Volkswagen issued more than $13 billion in bonds and asset-backed securities in US markets.

It said this was at a time when senior executives knew that more than 500,000 US diesel vehicles grossly exceeded legal vehicle emissions limits. 

Volkswagen "reaped hundreds of millions of dollars in benefit by issuing the securities at more attractive rates for the company," the SEC said.

It adding that VW "repeatedly lied to and misled US investors, consumers, and regulators as part of an illegal scheme to sell its purportedly 'clean diesel' cars and billions of dollars of corporate bonds and other securities in the US." 

The suit seeks to bar Winterkorn from serving as an officer or director of a public US company and recover "ill-gotten gains" along with civil penalties and interest. 

Winterkorn, who resigned days after the scandal became public in September 2015, was charged by US prosecutors in 2018 and accused of conspiring to cover up the German automaker's diesel emissions cheating. 

He remains in Germany. 

Volkswagen said in a statement the SEC complaint "is legally and factually flawed, and Volkswagen will contest it vigorously. 

"The SEC has brought an unprecedented complaint over securities sold only to sophisticated investors who were not harmed and received all payments of interest and principal in full and on time," the company said. 

The car maker added that the SEC "does not charge that any person involved in the bond issuance knew that Volkswagen diesel vehicles did not comply with US emissions rules when these securities were sold" but repeats claims about Winterkorn "who played no part in the sales". 

Volkswagen has agreed to pay more than $25 billion in the US in connection with the three-and-a-half-year old scandal, paying claims from owners, environmental regulators, states and dealers, and has offered to buy back about 500,000 polluting US vehicles. 

That figure included $4.3 billion in US criminal and civil fines. 

But the SEC said VW "has never repaid the hundreds of millions of dollars in benefit it fraudulently obtained." 

VW admitted in September 2015 to secretly installing software in 500,000 US vehicles to cheat government exhaust emissions tests and pleaded guilty in 2017 to felony charges.

In total, 13 people have been charged in the US, including Winterkorn and four Audi managers.