The series of wild swings in Eurotunnel’s share price this week has sparked calls for an investigation into claims that rumours had been spread in an attempt to drive up the share price.

With analysts unable to explain consecutive rises of almost 100 per cent, the French stock market regulator was asked to investigate.

Behind the calls is concern that speculators exploited the tensions created by what is only a small free float.

With 87.29 per cent of the share owners agreeing to swap their holding for a stake in the new company, Groupe Eurotunnel, theoretically less than 13 per cent of the capital was available on the market.

In practice, much of this has been blocked by small French investors who are refusing to sell, either because they want to retain free cross-channel travel or because they are fed up with the whole process.

Demand for the shares has been strong for two reasons.

On the one hand, many shareholders appear to have taken fright at reports earlier this month that the rescue package would fail and the operator faced bankruptcy.

In a panic move, they sold shares that they had agreed to swap for a stake in the new group – and they now need to buy them back.

On the other hand, investors have been buying up stock in the hope that Groupe Eurotunnel will soon became the target for a takeover bid.

The French construction group, Vinci, for instance, was said to have been snapping up stock, a rumour it has denied.

But as Eurotunnel’s share price rose, analysts warned that it exceeded the value of the company and will fall.

Robert Corden of Charles Stanley described the dramatic rise as “peculiar”.

Colette Neuville, chairwoman of the French Association of Small Shareholders, called on the French Financial Markets Authority to investigate. She believes that takeover rumours were spread to provoke frenetic activity. “It seems abnormal to me that the share price can vary in such proportions,” she said.

Eurotunnel has refused to comment on reports that executives are braced for a raft of takeover approaches once restructuring is complete.

Passing through

—Eurotunnel owns a 100-year concession until 2086 to operate the tunnel

—195m passengers and 176m tonnes of freight have passed through it so far

—The group runs 25 shuttle trains daily and earns revenue from Eurostar

—Last year it carried 2m cars, 1.3m lorries and 67,000 coaches

Times Recommends

• Lies and cover-up at MG Rover exposed by report
• High oil prices push manufacturing costs up
• Primark founder steps down as chief executive