HONGKONG (Reuters) - Britain said on Wednesday it was likely to consider whether it needed to block British firms exporting tear gas to Hong Kong after police there used it against pro-democracy protesters.

Britain disclosed it was reviewing the matter as some 200 protesters marched to the home of Hong Kong's Beijing-backed leader to push their case for greater democracy.

Police in the former British colony used tear gas against protesters on Sept. 28 sparking outrage among many residents of the Chinese-controlled city, an episode that prompted a surge in support for demonstrators.

"Yes, we have previously licensed exports of tear gas to Hong Kong," Mr Hugo Swire, a Foreign Office minister, said during a parliamentary debate on Hong Kong on Wednesday.

"But we would certainly take the recent disturbances in Hong Kong into account when these matters are discussed," he said, saying the government was likely to review whether recent events meant it should withdraw its approval for export licences.