The stock tumbled 4.71 per cent to settle at Rs 19.20 on BSE. During the day, it dipped 9.42 per cent to Rs 18.25.
At NSE, it fell 4.72 per cent to end at Rs 19.15.
The stock had lost over 11 per cent in the previous session also.
In further clampdown on Mallya, PNB has declared him as well as his group firms UB Holdings (UBHL) and the now-defunct Kingfisher Airlines as "wilful defaulter".
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PNB is the third public sector bank to declare the air carrier and its two guarantors - United Breweries (Holdings) Ltd and the flamboyant Mallya - as wilful defaulters. Earlier, United Bank of India and SBI had done the same.
PNB through a letter dated February 11 has declared the company a "wilful defaulter", UBHL said in a BSE filing yesterday, adding it received the letter on Monday.
"The company is in consultation with its legal counsel to challenge the decision by taking appropriate legal action that may be required in this regard," UBHL said on its future course of action.