Philippines President Rodrigo Duterte has inadvertently admitted to using hundreds of social media users to support him during his election campaign last year.

The controversial head of state, who has often stirred criticism for his tough policies condemned by human rights groups, made the remark during his address to the nation on Monday (24 June)

Duterte was defending himself against an Oxford University study, published earlier hits year, which claimed he had employed between 400 and 500 "keyboard trolls" during the May 2016 electoral campaign, keeping them even after his victory.

"Sometimes, when political parties or candidates use social media manipulation as part of their campaign strategy, these tactics are continued when they assume power," read the study.

"For example, in the Philippines, many of the so‐called 'keyboard trolls' hired to spread propaganda for presidential candidate Duterte during the election continue to spread and amplify messages in support of his policies now he's in power," it further claimed.

However, Duterte denied the allegations, labelling Oxford University as a "school for the stupid people", local media said.

"I spent P10 million? [$200,000; £153,539] Me? Maybe in the election. In the elections, more than that... And they were all during the campaign. [But now, I do not need it]. I do not need to defend myself from attacks. I've stated my peace during my inauguration and during the campaign. I am not anymore eligible for reelection," Duterte said, according to the Manila Times.

" [I have followers]," the president added, mentioning Margaux "Mocha" Uson, whom he appointed as assistant secretary for the Presidential Communications Operations Office.

He was also quoted by ABS-CBN News as saying: "I do not need to defend myself from attacks... I do not care if my ratings go up or down."

Duterte, who took office last June, is serving a six-year term, which cannot be renewed.

After being elected, the president stirred criticism for his infamous war on drugs, which has resulted in the death of at least 7,000 people across the country in the past 12 months.

During his address, the president vowed he would not stop his war on drugs in spite of mounting international criticism.

"Do not try to scare me with prison or the International Court of Justice," he said. "I'm willing to go to prison for the rest of my life."

"The fight will be unremitting as it will be unrelenting. There is a jungle out there, there are beasts out there preying on the innocent, the helpless," Duterte continued.

Duterte State of the Nation address
Philippine President Rodrigo Duterte gestures as he delivers his State of the Nation addressNoel Celis/AFP