Republican presidential nominee Donald Trump has suggested the US government has let illegal immigrants "pour into" the country so they can vote Democrat in the election.

His comments were made in a meeting with vice president of the union for border patrol agents, Art del Cueto, in New York on 7 October and reported by Reid Epstein for Wall Street Journal, pool report.

Cueto allegedly suggested border patrol agents had been told not to deport undocumented immigrants with criminal records, the pool report alleged, with the union vice president stating those people had been permitted to stay in the country "so they can vote".

Trump then responded: "They are letting people pour into this country so they can vote", The Hill reported.

Tighter border controls is a key issue Trump is campaigning on – with his suggestion to build a wall on the country's southern border with Mexico and plan to temporarily ban all Muslims from entering the country; just two ways the nominee has suggested tackling undocumented immigration and terrorism.

His suggestions have been roundly criticized as racially insensitive, in particular his comments that Mexico was "sending rapists" to the US. Hence, his latest comments are not likely to come as a surprise to voters.

Trump did not go into any detail about how an undocumented person would be able to vote in the US election and has not made any further comments on the subject since his exchange with the border patrol union was reported.