MORE than 100 MPs have voiced “grave concern” over Donald Trump’s Cuba oil blockade, calling on PM Sir Keir Starmer to oppose the US president’s “collective punishment” of its civilian population.Ministers were urged to reject Washington’s threat to slap tariffs on any other country that ships fuel to the island after it kidnapped Venezuelan leader Nicolas Maduro in January.The US has blocked Venezuelan oil supplies to Cuba’s socialist government, which said last week that it had not received any ​fuel in three months.