Former prime minister Nawaz Sharif and his daughter Maryam Nawaz on Wednesday left for London where Sharif's wife Kulsoom Nawaz is undergoing treatment for lymphoma.

The father-daughter duo, who are currently facing accountability hearings, left for London on a Qatar Airlines flight around 9:30am and are scheduled to return on April 22.

However, in a tweet just before departure, Maryam vowed to return before the next hearing if they are not granted an exemption from appearance by the accountability court where proceedings in the Avenfield Properties reference are underway.

"My mother is hospitalised again," she had tweeted a day earlier, with a request for prayers for her mother. The family had also issued a statement informing that the two would leave for London to see the ailing Kulsoom.

Begum Kulsoom had undergone a surgery for lymphoma (throat cancer). The PML-N had declared the procedure successful, but of late her condition deteriorated and she was hospitalised.

Last week, the National Accountability Bureau had claimed in a report that the PML-N government had shown reluctance to place the names of Nawaz Sharif and other members of his family on the Exit Control List (ECL) on the bureau's request.

NAB had asked the interior ministry to put on the ECL the names of Nawaz Sharif, his children — Maryam, Hassan and Hussain — and his son-in-law retired Capt Safdar.

All of them are being tried in accountability courts regarding references filed following the Supreme Court's orders in Panamagate case.

Sharif's sons are already in London and have been declared proclaimed offenders by the accountability court in the corruption references against them.