The outraged protesters took to the streets in Sitra, which is close to the UK base, chanting slogans against such an expansion, press tv reported.
Meanwhile, Bahraini opposition figures, including members of the main opposition party, al-Wefaq National Islamic Society, expressed deep concern over the increase of foreign military presence in the Persian Gulf kingdom.
Al-Wefaq argues that the agreement would transform the country into a main base for foreign military operations in the region.
Nabeel Rajab, an opposition politician and president of the Bahrain Center for Human Rights, also described the base as "a reward to the British government for the silence they provided on human rights abuses in Bahrain, and for their continued support of this tyrannical and corrupt regime".
The pact will give Britain the go-ahead to reinforce its onshore facilities at the Mina Salman Port in Bahrain, where the UK permanently stations four mine-hunter warships, British Defense Secretary Michael Fallon said on Friday.
The base, which provides support for British destroyers and frigates in the Persian Gulf, will now be expanded to include a new forward operating base and a place to plan, store equipment for naval operations and accommodate Royal Navy personnel.
Bahraini Foreign Minister Sheikh Khalid has claimed the new base is part of a deal with the United Kingdom to maintain regional security and stability in the face of challenging circumstances and noted that Manama is looking forward to the early implementation of this agreement.
The Arab sheikhdom, which has been witnessing bloody anti-regime protests since 2011, also hosts the Fifth Fleet of the US Navy. The base provides protection to the Bahraini royal family and also ensures the US dominance in the oil-rich region.
Over the past four years, thousands of anti-regime protesters have held numerous demonstrations in the streets of Bahrain, calling for the Al Khalifa royal family to relinquish power.
Many Bahrainis have been tortured or killed and hundreds more injured and arrested during the regime’s ongoing crackdown on peaceful demonstrations.
However, the UK and the US have continued support for the Bahraini government and kept silence over Manama regime’s violent crackdown on the popular protests.
In October, Bahraini Prince Nasser bin Hamad Al Khalifa, who is accused of involvement in torturing protesters in his home country, travelled to London to visit a Royal British Navy transport dock and appeared at the 2014 British Invention Show.
Manama also continues to receive military support on the ground form Saudi Arabia and some other Arab monarchies of the Persian Gulf region.
On March 14, 2011, troops from Saudi Arabia and the United Arab Emirates were deployed to Bahrain to assist the Al Khalifa regime in its crackdown on peaceful protests in the country.