The Economic and Development Affairs Authority "will boost coherence, integration and coordination between member states in all economic and development sectors," the Gulf Cooperation Council said in a statement after a summit in Jeddah, Saudi Arabia.
The GCC was founded in 1981 to more deeply integrate the Gulf countries, but analysts say progress has been slow.
The collapse of global oil prices has forced the Gulf monarchies to make unprecedented fuel and energy subsidy cuts and plan to introduce indirect taxation. They have also scaled back spending on large projects.
Oil prices have fallen from more than $100 a barrel in early 2014 to around half that level.
The newly formed body "will look into matters such as completing the customs union and the common market of the GCC states", Saudi Foreign Minister Adel al-Jubeir told a news conference after the summit.
He said the authority "can solve these issues urgently and effectively" to promote cooperation.
No decision has been made on when to start using a single Gulf currency, which has been mooted for years, GCC Secretary General Abdullatif al-Zayani said.
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After a summit with the GCC in Riyadh last month, US President Barack Obama said the six-nation GCC will establish a "high-level economic dialogue" with the United States.
It will "focus on adjusting to lower oil prices, increasing our economic ties and supporting GCC reforms", Obama said.
Along with Saudi Arabia, the world's biggest oil exporter and largest Arab economy, the GCC includes Bahrain, Kuwait, Oman, Qatar and the United Arab Emirates.
Emirs and kings of the Gulf also decided to hold an annual summit with the British prime minister "to strengthen and intensify cooperation", Jubeir said.
With the United States and France, Britain is a major weapons supplier to Saudi Arabia.
French President Francois Hollande last year became the first Western leader to attend a GCC summit, which was held in the Saudi capital.
Riyadh has been deepening ties with major powers beyond its traditional security partner the United States.
Gulf ties with Washington have been strained over how to deal with Shiite Iran, regional rival of the Sunni-dominated Gulf.