The 1649 Programme of five additional warships for the Navy of the new English Commonwealth ("to be frigate fashion") was approved by the Council of State on 25 March 1649, less that two months after the execution of King Charles I and the creation of a republican government.

Three of these frigates, intended to be classed as Fourth rates, were ordered in late March (although of these the Worcester would be delayed and altered while building to a Third rate), while on 12 April orders were placed for two larger Third rates to serve as flagships for the Winter Guard (Speaker and Fairfax).

[1] The construction of the vessels was assigned to the state dockyards.

The ships would be designed by and built under the supervision of the Master Shipwright of each Dockyard.

The dimensions and armament of these various frigates was so varied that it will be listed in the articles on the individual vessels.