Mr Ibrahim has in the past made allegations of vote-rigging, which the government strongly rejects.
But Mr Khan added that his party was collecting evidence of alleged vote-rigging.
The regulator argues that splitting up a chunk of shares just to push through the deal amounts to illicit vote-rigging.
Sunday's partial re-run of the vote in Karachi was ordered after Mr Khan's party accused the MQM of widespread vote-rigging and intimidation.
The measures follow allegations of widespread electoral fraud, including vote-rigging, in the UK since postal and proxy voting were greatly extended in 2001.
BBC: NEWS | UK | UK Politics | Election night dramas 'will stay'
The EU has said it would investigate claims by one observer of vote-rigging in Cabinda, but other observers have said the vote was transparent.
Vote-rigging by President Ferdinand Marcos led to his downfall in 1986.
But the system was introduced with one main purpose - to eliminate the possibility of vote-rigging, and give the Kenyan electorate faith in the credibility of the count.
French papers warn of a crisis in the conservative opposition Union for a Popular Movement (UMP) after a "grotesque" leadership contest failed to produce a clear winner amid claims of vote-rigging.
But rumors of a comeback have intensified since the UMP's confused attempt to elect a successor last November, in which both candidates Francois Fillon and Jean-Francois Cope claimed victory amid intraparty squabbling and allegations of vote-rigging.
In a riposte to Mr Yushchenko's allegations (backed by western election observers) of vote-rigging in Mr Yanukovich's power base in the Russian-speaking east of Ukraine, Mr Yanukovich has alleged ballot-stuffing in Mr Yushchenko's Ukrainian-speaking stronghold in the west, and has filed his own complaint to the Supreme Court.
Those elections were considered fairly credible but with more at stake this time, will politicians be able to resist the "mago-mago", or vote rigging, of elections past, asks the BBC's Caroline Duffield in Lagos.
To a fresh observer, it was the very opposite of what you might expect a Nigerian election to be - an escape from the grotesque abuses of ballot stuffing and vote rigging of the past.
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