Hamid Mir, who hosts a prime-time show on Geo television, was criticised by the Taliban last month in the wake of the shooting of teenage activist Malala Yousafzai.
"Life and death is in the hands of Allah. Allah saved his life but we will make a similar attempt again," TTP spokesman Ehsanullah Ehsan told AFP by telephone from an unknown location.
"Hamid Mir earlier shot into prominence for working in the interest of Islam and Muslims. We targeted him because now he is working against Islam and Muslims," he said.
Police said the device - half a kilogram of explosives fitted with a detonator - was found stuck under his car in Islamabad on Monday.
Interior Minister Rehman Malik offered a cash reward of Rs50 million for anyone with information about who was responsible for the powerful bomb.
Malala calls Mir
Mir sent out a tweet on Monday saying that 15-year-old Malala Yousafzai, who was shot by the Taliban, called him to express solidarity.
The tweet read:
Malala Yousafzai and her father just called me from UK and expressed their solidarity. Malala said that Insha Allah we will defeat terrorists.
Taliban hitmen shot Malala on her school bus in Swat Valley because she had campaigned for girls' rights to education. The 15-year-old survived and is currently under treatment at a hospital in Birmingham.
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