Traders are bracing for more big price swings in the pound between now and the expected 31 October Brexit date after Britain's prime minister Boris Johnson moved to suspend parliament, with a volatility gauge hitting its highest level of 2019.

Mr Johnson yesterday announced plans to suspend parliament for more than a month from early September.

The move has outraged his opponents as it limits the time available to prevent Britain exiting the European Union without a divorce deal on 31 October. It also raises the chances he will face a vote of no confidence and possibly a national election.

Three-month sterling implied volatility - a gauge measuring expected price swings in the pound between now and end-November- rocketed to its highest since December. The one-month measure rose to a four-month high while the six-month gauge was at its most elevated since January.

The pound fell sharply yesterday as Mr Johnson's move threw down the gauntlet to his opponents to try to bring his government down, or step aside as he pursued his "do or die" Brexit policy by 31 October.

Mr Johnson has defended the suspension and said there will be plenty of time for lawmakers to debate Brexit.

It remained weak today, trading down 0.1% at $1.2195 by 3.30pm. It was neutral against the euro however at 90.69 pence.

"This price action reflects concerns that the little time that remains for parliament to attempt to block a no-deal Brexit will now be even shorter," said Lee Hardman, currency analyst at MUFG.

The pound's decline has been relatively modest this week because most investors already thought a no-deal Brexit was the most likely outcome, judging by positioning data and derivatives pricing, analysts said.

Traders said much of the action was in investors rushing to protect themselves from more volatility rather than placing bets on further falls in the currency.

Risk reversals - the skew between put and call options - suggest traders see the pound as more likely to fall than rise in the next three months, but they are not as bearish as they were earlier this month.

Most members of parliament oppose a no-deal Brexit and they still have some time to call a vote of no confidence, but Mr Johnson is not bound by law to resign, which complicates things further, analysts say.

Parliament reopens for business on 3 September, but will be "prorogued" - suspended - the following week until 14 October.

However, if a Brexit deal is agreed on before the deadline or if Britain and the EU were to agree to put back the departure date by extending the so-called Article 50, the pound could strengthen sharply as there are no barriers to prevent it doing so, analysts say.

"Despite the noise, the poor mood music and proroguing, the path of least resistance is still for sterling topside as a lot of the negativity is in the price," said Jordan Rochester, currency analyst at Nomura.

"But (pro-EU) Remainer MPs have to act fast and swiftly for this tactical trade to become longer term," Rochester said, adding the bank held a short euro/sterling position.