Former house speaker Newt Gingrich has spoken out against Barack Obama, suggesting race relations have become worse 'under a black president' and calling him 'fairly pathetic'.

Gingrich, who was a favourite on Donald Trump's VP shortlist but was passed over in favour of Indiana governor Mike Pence, said the president had hit out at police and needed a better strategy to deal with violence in the country.

"As long as we have Barack Obama doing what he did over the last few years, if you've had seven-and-a-half years of a black president, seven-and-a-half years of a black attorney general, Gallup reports race relations today are worse than any time in the last 17 years," Gingrich told MSNBC in an interview from the Republican Convention 2016.

"Why? Because how often has he hit the police," he added. "He hit the police in Cambridge and he was wrong. He hit the police in Ferguson, he was wrong. He hit the police about Florida, he was wrong.

"At what point does the president have some obligation, to say, you know – there are two parts of this. One, we've got to better understand the experience of being black in America and in places like Chicago, where 3,200 people have been killed in the Obama presidency, we had better have a strategy that works. We don't.

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"You could start with New York City which had reduced the murder rate by 85% from what it what when Giuliani went in, now nobody on the left wants to hear that. But you look at the number of thousands of people who would be alive today if Chicago had the New York strategy."

Gingrich, if elected to office, is widely expected to be given a role in Trump's team. He added that a New York strategy would, however, be seen as too intrusive as it took too many police officers on the beat.

"When you don't spend the money on cops, you spend the money on funerals," he said.

On Obama's speaking out in Dallas for policeman, he added it was 'fairly pathetic' that the president had only spoken out in support of police after seven and a half years as president.

Gingrich is expected to speak on the third day of the Republican Convention, when the theme will be 'make America first again'.