BP shares were up 4.3 per cent to 485.65 pence as the market opened.
The Daily Mail, citing sources close to the Anglo-Dutch group, reported Shell weighed an opportunistic bid for BP as crude gushed into the Gulf, but was discouraged by the potentially uncapped legal liabilities.
The Daily Mail had said Shell could yet bid for BP if another suitor emerged but Europe's largest oil company by market value was unlikely to be the "first mover."
Analysts and industry sources said during the crisis last summer it was likely that both US oil giant Exxon Mobil and Shell – the only companies considered large enough to mount a bid – would run the slide-rule over BP.
However, the two notoriously conservative companies were seen as likely to be discouraged by the open-ended nature of BP's liabilities.
Now BP's shares have rebounded 65 per cent from their June low at 296 pence, to give BP a market value of around $140bn (£89bn), a bid would be much harder to mount, especially for Shell which is worth over $210bn.
Exxon has a market value of almost $370bn.
It is uncertain whether regulators on either side of the Atlantic would support a tie-up in top tier of the industry.