LONDON, Mar. 25 (Reuters) - A convoy of tractors protested outside Britain's parliament on Monday against post-Brexit trade deals and what they called substandard food imports in the latest demonstrations by farmers globally.

At least 50 tractors, many with Union Jack flags and signs such as "no farmers, no food, no future", took part in the protest outside the Houses of Parliament.

The farmers are demanding that the government enforce more accurate food labelling and take steps to improve the country's food security.

They also want the government to end trade deals that they say are allowing imports of food produced to standards that would be illegal in Britain and undercut local farmers.

"Time and time again they have let us down," Liz Webster, founder of Save British Farming, told the BBC. "They promised to uphold our high standards and promised not to allow Britain to be a dumping ground ... what they are doing is making us a dumping ground."

The rally follows protests by farmers across Europe who are angered by competition from cheaper imports and want stricter environmental regulations.