A group of prominent Irish-Americans has called for a boycott of "Irish Lives Matter" t-shirts that are being sold in the US.

More than 60 leaders from Irish-America's civil, political and educational community have signed a letter mourning the passing of US Congressman and civil rights leader John Lewis, who died earlier this month at the age of 80.

The letter is being sent to Congresswoman Karen Bass, the chair of the Congressional Black Caucus, and calls for the support of the Black Lives Matter movement. 

It also urges Irish-Americans to boycott the sale of "Irish Lives Matter" t-shirts. 

Former Democratic Congressman Joe Crowley is one of the organisers of the letter. 

"I support the fight for racial justice and I oppose the sale of these t-shirts because they dilute and diminish the efforts of Black Lives Matter," Mr Crowley said. 

The "Irish Lives Matter" t-shirts are available for sale via Amazon, Walmart and other retailers. 

The letter urges a boycott of the products to protest against what is described as a "wrongheaded, commercial decision" to sell them.

"We believe the sale of these t-shirts is at best tone deaf and insensitive and at worst a deliberate, cynical attempt to trivialise, diminish or denigrate the BLM (Black Lives Matter) movement", the letter states.

Among those who signed the letter were the former Governor of Maryland Martin O'Malley, Congressman Richard Neal, Chair of the Friends of Ireland Caucus and former US Ambassador to Ireland Kevin O'Malley.