(Reuters) - U.S. government tax collections would get a multi-billion-dollar boost if President Barack Obama issued an executive order giving temporary legal status to millions of undocumented residents, the liberal-leaning Center for American Progress said in a report on Thursday.

The group, which has close ties to the Obama administration, estimated $21.2 billion in additional payroll taxes would be collected over five years under one scenario available to Obama, who has made immigration reform a priority of his second term.

That revenue increase is based on a scenario where 4.7 million undocumented immigrants receive temporary legal status,