David Cameron was expected to discuss the Bahrain authorities' crackdown on protesters with the Gulf state's Crown Prince when he visits Downing Street this evening.
The visit comes as US President Barack Obama makes an eagerly-anticipated speech on the events of the so-called Arab Spring, which saw protests against autocratic rulers in a range of countries in the Middle East and north Africa, including Bahrain.
Bahrain was widely condemned for inviting neighbouring Saudi Arabia to send in troops to help put down protests against the ruling al-Khalifa dynasty.
Crown Prince Salman al-Khalifa's visit to London comes after he declined an invitation to the wedding of Prince William and Princess Catherine last month amid fears that protests against his presence might tarnish the event.
Bahrain is due on June 1 to lift the martial law imposed in March following weeks of pro-democracy protests which resulted in the deaths of at least 29 people. Hundreds of people have been arrested and dozens put on trial in special courts.
Speaking ahead of the visit, Mr Cameron's official spokesman said: "I would expect them to discuss developments in the Middle East and north Africa, the Arab Spring, the Middle East peace process and the situation in Bahrain.
"Bahrain has been seeking to reform their political system in a number of ways, and that is something we welcome."
Asked at a regular daily press briefing in Westminster why Britain was welcoming the Crown Prince, when it had got involved in military action to prevent the repression of protesters in Libya, the spokesman said: "We said all along that the situation in different countries is different.
"There are different circumstances and we need to reflect that. Clearly, in all cases we would support reform and dialogue."
Human rights campaigner Peter Tatchell said: "It is a huge error of judgment to fete the Crown Prince of Bahrain at a time when his regime is arresting, jailing, torturing and killing peaceful democracy protesters.
"Britain should not be conducting business as usual with a tyranny that is guilty of gross human rights abuses.
"David Cameron should press the Bahraini authorities to lift the state of emergency immediately, halt the use of torture and release all political prisoners. Saudi Arabia and the UAE should be urged to withdraw their troops.
"If the duty to protect civilians applies in Libya, why not in Bahrain?"
Amnesty International UK director Kate Allen said: "The UK Government has talked about the immense significance of the Arab Spring and it's essential that it lives up to its own warm words on the importance of allowing peaceful protest in countries like Bahrain.
"David Cameron should use this opportunity to make it absolutely clear that the Bahraini government must end its relentless crackdown on human rights.
"The Prime Minister ought to make it abundantly clear to Sheikh Salman that Bahrain's relations with the UK will suffer if the Bahraini authorities refuse to allow peaceful protests or conduct proper investigations into numerous allegations that detained protesters have been tortured.
"It's vital that the Government doesn't overlook human rights abuse in Bahrain in any kind of effort to smooth the way to arms sales or trade more generally."
Former foreign minister Denis MacShane said Mr Cameron should not be "rolling out the red carpet for Bahrain's torturer-in-chief at Downing Street today".
The Rotherham MP urged William Hague in the Commons in February to suspend British arms sales to Bahrain and support the pro-democracy movement.
"We have well-documented reports of torture, including the torture of women doctors, killings, and even the Saudis sending tanks across to Bahrain to crush the protests in the time-honoured fashion of the Soviets in Prague or Budapest," said Mr MacShane.
"The Prime Minister is rightly calling for Gaddafi to go to the International Criminal Court but the Bahraini despots who are equally guilty of repression and torture and mass arrests are being given tea and a gentle talking-to in Downing Street. It is just sad that David Cameron has such a tin ear to the cries for freedom from the Arab world and is supping with the torturers not supporting the moves for democracy."Reuse content