New Delhi Television Ltd said a major stake sale by its founders to Adani group would require clearance from India’s tax authorities, adding another hurdle to the conglomerate’s bid to take control of the popular news network.

The income tax department in 2017 provisionally barred the founders Prannoy and Radhika Roy from selling a part of their stake as part of a reassessment of their taxes, NDTV said in an exchange filing late on Wednesday.

NDTV and Adani have locked horns in public after the conglomerate, run by India’s richest man, Gautam Adani, last week unveiled plans to control a majority stake in the news network, seen as a bastion of independent media.

Shares in NDTV rose to the maximum permitted limit of five per cent in morning trade on Thursday, marking their sixth straight day of gains after Adani’s announcement. The shares are currently trading at their highest level in more than 14 years.

Adani has tried to execute the takeover plan by acquiring a little known Indian company that gave four billion rupees ($50 million) in loans to NDTV’s founders more than a decade ago in exchange for warrants that allowed it to buy a stake in the news group at any time.

Adani Group said last week it had exercised those rights, which NDTV said was done without its consent.

NDTV said on Wednesday tax authorities were already reviewing whether the loans gave rise to an estimated capital gains tax obligation of 1.75bn rupees based on allegations that they amounted to a transfer of the controlling interest in the network.

NDTV said it had invited the Adani group’s company to join its application to the tax authorities for clarification. India’s tax authorities and the Adani group did not immediately respond to requests for comment.

Both sides have also separately asked the market regulator whether the Roys were restricted from selling the stake by a previous prohibition on them dealing in India’s securities market. That prohibition followed their being investigated for insider trading.

NDTV is regarded by some as one of the few independent voices in India’s rapidly polarising media landscape, and the takeover attempt has triggered concerns among journalists and politicians that a change of ownership could undermine its editorial integrity.